【mysql 01】查詢–總結
/* ?*?本程序專為總結MySQL而寫！ ?*?@author?kevinelstri ?*?@time?2016/7/14 ?*?*/ package?Database; public?class?Database01?{ ????public?static?void?main(String[]?args){ ????????System.out.println("本程序專為總結MySQL而寫！"); ????/*? ?????*?--------------------------------------------MySQL基本操作------------------------------------------------- ?????*? ?????*?mysql的啟動：mysql?-u?root?-p ?????*?mysql服務開啟：net?start?mysql ?????*?mysql服務關閉：net?stop?mysql ?????*? ?????*?創建數據庫：create?database?db_name; ?????*? ?????*?查看所有數據庫：show?databases; ?????*? ?????*?查看某一個數據庫：show?create?database?db_name; ?????*? ?????*?刪除數據庫：drop?database?db_name; ?????*? ?????*?修改數據庫：alter?database?db_name[修改指令]; ?????*? ?????*?創建表：create?table?db_name; ?????*?????在表的創建過程中，至少包括一個屬性： ?????*?????create?table?test.class(?//使用test.class表示在數據庫test中創建一個class表 ?????*?????class_no?varchar(20);????//創建表的過程中，至少要創建一個屬性 ?????*?????data_time?date ?????*?????); ?????*????? ?????*?使用數據庫：use?db_name;//表示在接下來的過程中都會使用這個數據庫 ?????*? ?????*?查看數據庫中的表：show?tables;//查看使用的數據庫中的所有的表 ?????*? ?????*?獲取具有某種規則的表：show?table?[like?'%']; ?????*? ?????*?查看某個表的創建信息：show?create?table?exam_student; ?????*??????????????????????show?create?table?exam_studentG; ?????*? ?????*?查看表的結構：describe?table_name; ?????*??????????????desc?table_name; ?????*?????????????? ?????*?刪除表：drop?table?table_name; ?????*? ?????*?修改表名：rename?table?old_table_name?to?new_table_name; ?????*? ?????*?crud:增刪改查（create、retrieve、update、delete） ?????*? ?????*?創建數據/插入數據：insert?into?表名?(字段列表)?values?(值列表) ?????*?????????insert?into?exam_table?(name,stu_no)?values?('Mary',001); ?????*????????? ?????*?查詢數據：select?(字段列表)?from?表名??查詢條件 ?????*??????????select?(name,stu_no)?from?exam_student?where?stu_no?>?002; ?????*??????????select?*?from?exam_student; ?????*?????????? ?????*?????????? ?????*?刪除數據：delete?from?exam_student?where?stu_no=1;??? ?????*? ?????*?修改數據：update?表名?set?字段=新值....條件 ?????*??????????update?exam_student?set?score=90?where?stu_no='002'; ?????*??????????update?exam_student?set?name='Lily'?where?stu_no='001'; ?????*? ?????*?查看變量：show?variables; ?????*? ?????*?-------------------------------------------MySQL高級操作----------------------------------------- ?????*? ?????*?【distinct】查詢不重復數據：select?distinct?country?from?website; ?????*???????//注意?distinct的用法，使重復元素只顯示一次 ?????*? ?????*?【where】子句：select?*?from?website?where?id=1; ?????*??????//where子句查詢特定條件的數據 ?????*??????select?name?from?website?where?country='CN'; ?????*? ?????*?【and?or】子句：select?*?from?website?where?country='CN'; ?????*?????????????+------+---------+-----------------------+-------+---------+ ?????*?????????????|?id???|?name????|?url???????????????????|?alexa?|?country?| ?????*?????????????+------+---------+-----------------------+-------+---------+ ?????*?????????????|????2?|?taobao??|?http://www.taobao.com?|????13?|?CN??????| ?????*?????????????|????3?|?cainiao?|?http://www.runoob.com?|???673?|?CN??????| ?????*?????????????|????4?|?weibo???|?http://weibo.com??????|????20?|?CN??????| ?????*?????????????+------+---------+-----------------------+-------+---------+ ?????*? ?????*???????????select?*?from?website?where?country='CN'?or?country='USA';?//or是或者關系? ?????*?????????????+------+----------+-------------------------+-------+---------+ ?????*?????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ?????*?????????????+------+----------+-------------------------+-------+---------+ ?????*?????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ?????*?????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ?????*?????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ?????*?????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ?????*?????????????|????5?|?Facebook?|?http://www.facebook.com?|????20?|?USA?????| ?????*?????????????+------+----------+-------------------------+-------+---------+ ?????*???????????select?*?from?website?where?country='CN'?and?country='USA';//and并集關系 ?????*???????????Empty?set?(0.15?sec) ?????*? ?????*???????????select?*?from?website?where?alexa>15?and?(country='CN'?or?country='USA'); ???????????????????+------+----------+-------------------------+-------+---------+???????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ???????????????????+------+----------+-------------------------+-------+---------+???????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ???????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ???????????????????|????5?|?Facebook?|?http://www.facebook.com?|????20?|?USA?????| ???????????????????+------+----------+-------------------------+-------+---------+ ?????*? ?????*?【order?by】排序：desc逆序排列,asc正序排列 ?????*??????????select?*?from?website?order?by?name?desc;//按姓名逆序排列 ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????????|????5?|?Facebook?|?http://www.facebook.com?|????20?|?USA?????| ????????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????????+------+----------+-------------------------+-------+---------+????????????????????5?rows?in?set?(0.18?sec) ????????????????select?*?from?website?order?by?name?asc;//按姓名正序排列 ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????????|????5?|?Facebook?|?http://www.facebook.com?|????20?|?USA?????| ????????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????????+------+----------+-------------------------+-------+---------+ ?????*? ?????*? ?????*?【update】更新表中的數據：mysql>?update?website ?????*??????????????????????????->?set?alexa=32,country='CN' ?????*??????????????????????????->?where?id=7; ?????*??????? ?????*??????????mysql>?select?*?from?website; ????????????????+------+----------+-------------------------+-------+---------+????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????+------+----------+-------------------------+-------+---------+????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????| ????????????????+------+----------+-------------------------+-------+---------+ ?????*? ?????*? ?????*? ?????*?【delete】刪除行： ?????*??????????delete?from?website?where?name='baidu'; ?????*? ?????*??????????select?*?from?website; ?????*??????????+------+----------+-------------------------+-------+---------+????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????+------+----------+-------------------------+-------+---------+????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????|????7?|?ali??????|?http://www.ali.com??????|??NULL?|?NULL????| ????????????????+------+----------+-------------------------+-------+---------+ ?????*? ?????*? ?????*?【like】操作符用于在where子句中搜索列中的指定模式： ?????*??????????select?*?from?website?where?url?like?'http://www%'; ?????*??????????+------+----------+-------------------------+-------+---------+????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????+------+----------+-------------------------+-------+---------+????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????| ????????????????+------+----------+-------------------------+-------+---------+ ?????*? ?????*??????????select?name,url?from?website?where?name?like?'%o'; ?????*??????????+---------+-----------------------+????????????????|?name????|?url???????????????????| ????????????????+---------+-----------------------+????????????????|?taobao??|?http://www.taobao.com?| ????????????????|?cainiao?|?http://www.runoob.com?| ????????????????|?weibo???|?http://weibo.com??????| ????????????????+---------+-----------------------+ ?????*? ?????*? ?????*??????????mysql>?select?name,url?from?website?where?name?not?like?'%o'; ????????????????+----------+-------------------------+????????????????|?name?????|?url?????????????????????| ????????????????+----------+-------------------------+????????????????|?Google???|?http://www.google.com???| ????????????????|?Facebook?|?http://www.facebook.com?| ????????????????|?ali??????|?http://www.ali.com??????| ????????????????+----------+-------------------------+ ?????*? ?????*?【通配符】：? ?????*??????????+----------+---------------------------+????????????????|??????%???????|?替代?0?個或多個字符??????????????| ????????????????+----------+---------------------------+????????????????|??????_???????|?替代一個字符?????????????????????????????| ????????????????+----------+---------------------------+????????????????|????[a-z]?????|?a-z中的任何單一字符???????????| ????????????????+----------+---------------------------+????????????????|[^a-z]/[!a-z]?|?不在a-z中的任何單一字符?| ????????????????+----------+---------------------------+ ?????*? ?????*???????mysql>?select?*?from?website?where?name?like?'_o%'; ????????????????+------+--------+-----------------------+-------+---------+????????????????|?id???|?name???|?url???????????????????|?alexa?|?country?| ????????????????+------+--------+-----------------------+-------+---------+????????????????|????1?|?Google?|?http://www.google.com?|?????1?|?USA?????| ????????????????+------+--------+-----------------------+-------+---------+ ?????*? ?????*???????mysql>?select?name?from?website?where?name?like?'__i%';//這里是兩個下劃線 ????????????????+---------+????????????????|?name????| ????????????????+---------+????????????????|?cainiao?| ????????????????|?weibo???| ????????????????|?ali?????| ????????????????+---------+ ?????*? ?????*?【in】操作符：允許在where子句中規定多個值，where條件在某個范圍內 ?????*? ?????*????????mysql>?select?*?from?website ??????????????????->?where?alexa?in?(1,2,3,4,5,6,7,8,9,0); ????????????????+------+----------+-------------------------+-------+---------+????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????+------+----------+-------------------------+-------+---------+????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????+------+----------+-------------------------+-------+---------+ ?????*? ?????*????????mysql>?select?name?from?website?where?name?in?('google','facebook','baidu','ali'); ????????????????+----------+????????????????|?name?????|???注意：mysql中對大小寫不敏感，所以在命名的時候要注意大寫和小寫是一樣的 ????????????????+----------+????????????????|?Google???| ????????????????|?Facebook?| ????????????????|?ali??????| ????????????????+----------+ ?????*? ?????*?【between】操作符：選取介于兩個值之間的數據范圍內的值。這些值可以是數值、文本或者日期。 ?????*????????mysql>?select?*?from?website?where?alexa?between?1?and?50;//數值 ????????????????+------+----------+-------------------------+-------+---------+????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????+------+----------+-------------------------+-------+---------+????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????| ????????????????+------+----------+-------------------------+-------+---------+ ?????*? ?????*????????mysql>?select?*?from?website?where?name?between?'a'?and?'f';//文本，name的第一個字母的范圍 ????????????????+------+---------+-----------------------+-------+---------+????????????????|?id???|?name????|?url???????????????????|?alexa?|?country?| ????????????????+------+---------+-----------------------+-------+---------+????????????????|????3?|?cainiao?|?http://www.runoob.com?|???673?|?CN??????| ????????????????|????7?|?ali?????|?http://www.ali.com????|????32?|?CN??????| ????????????????+------+---------+-----------------------+-------+---------+ ?????*? ?????*????????mysql>?select?*?from?website?where?alexa?not?between?1?and?20; ????????????????+------+---------+-----------------------+-------+---------+????????????????|?id???|?name????|?url???????????????????|?alexa?|?country?| ????????????????+------+---------+-----------------------+-------+---------+????????????????|????3?|?cainiao?|?http://www.runoob.com?|???673?|?CN??????| ????????????????|????7?|?ali?????|?http://www.ali.com????|????32?|?CN??????| ????????????????+------+---------+-----------------------+-------+---------+ ?????* ?????*????????mysql>?select?*?from?website?where?(alexa?between?1?and?20)?and?country?not?in?('CN'); ????????????????+------+----------+-------------------------+-------+---------+????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????+------+----------+-------------------------+-------+---------+????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????+------+----------+-------------------------+-------+---------+ ?????* ?????*????????mysql>?select?*?from?access_log?where?date?between?'2016-05-15'?and?'2016-05-17'; ????????????????+------+---------+-------+------------+????????????????|?aid??|?site_id?|?count?|?date???????| ????????????????+------+---------+-------+------------+????????????????|????6?|???????4?|????13?|?2016-05-15?| ????????????????|????7?|???????3?|???220?|?2016-05-16?| ????????????????|????8?|???????5?|???545?|?2016-05-16?| ????????????????|????9?|???????3?|???201?|?2016-05-17?| ????????????????+------+---------+-------+------------+ ?????*?????????????? ?????* ?????*????????mysql>?select?*?from?access_log; ????????????????+------+---------+-------+------------+????????????????|?aid??|?site_id?|?count?|?date???????| ????????????????+------+---------+-------+------------+????????????????|????1?|???????1?|????45?|?2016-05-10?| ????????????????|????2?|???????3?|???100?|?2016-05-13?| ????????????????|????3?|???????1?|???230?|?2016-05-14?| ????????????????|????4?|???????2?|????10?|?2016-05-14?| ????????????????|????5?|???????5?|???206?|?2016-05-14?| ????????????????|????6?|???????4?|????13?|?2016-05-15?| ????????????????|????7?|???????3?|???220?|?2016-05-16?| ????????????????|????8?|???????5?|???545?|?2016-05-16?| ????????????????|????9?|???????3?|???201?|?2016-05-17?| ????????????????+------+---------+-------+------------+ ?????* ?????* ?????* ?????*???????請注意!!!，在不同的數據庫中，BETWEEN?操作符會產生不同的結果！ ????????????????在某些數據庫中，BETWEEN?選取介于兩個值之間但不包括兩個測試值的字段。 ????????????????在某些數據庫中，BETWEEN?選取介于兩個值之間且包括兩個測試值的字段。 ????????????????在某些數據庫中，BETWEEN?選取介于兩個值之間且包括第一個測試值但不包括最后一個測試值的字段。 ????????????????因此，請檢查您的數據庫是如何處理?BETWEEN?操作符！ ?????* ?????*??【AS】:別名，可以為表名稱或列名稱指定別名。 ?????* ?????*?????列的別名： ?????*??????mysql>?select?aid,site_id?as?id,count,date??//別名是在查詢時，指定的別名 ????????????????->?from?access_log; ????????????????+------+------+-------+------------+????????????????|?aid??|?id???|?count?|?date???????| ????????????????+------+------+-------+------------+????????????????|????1?|????1?|????45?|?2016-05-10?| ????????????????|????2?|????3?|???100?|?2016-05-13?| ????????????????|????3?|????1?|???230?|?2016-05-14?| ????????????????|????4?|????2?|????10?|?2016-05-14?| ????????????????|????5?|????5?|???206?|?2016-05-14?| ????????????????|????6?|????4?|????13?|?2016-05-15?| ????????????????|????7?|????3?|???220?|?2016-05-16?| ????????????????|????8?|????5?|???545?|?2016-05-16?| ????????????????|????9?|????3?|???201?|?2016-05-17?| ????????????????+------+------+-------+------------+ ?????* ?????*?????表的別名： ?????*??????mysql>?select?w.name,w.url,a.count,a.date ????????????????->?from?website?as?w,access_log?as?a??//對表進行別名定義 ????????????????->?where?a.site_id=w.id; ????????????????+----------+-------------------------+-------+------------+????????????????|?name?????|?url?????????????????????|?count?|?date???????| ????????????????+----------+-------------------------+-------+------------+????????????????|?Google???|?http://www.google.com???|????45?|?2016-05-10?| ????????????????|?cainiao??|?http://www.runoob.com???|???100?|?2016-05-13?| ????????????????|?Google???|?http://www.google.com???|???230?|?2016-05-14?| ????????????????|?taobao???|?http://www.taobao.com???|????10?|?2016-05-14?| ????????????????|?Facebook?|?http://www.facebook.com?|???206?|?2016-05-14?| ????????????????|?weibo????|?http://weibo.com????????|????13?|?2016-05-15?| ????????????????|?cainiao??|?http://www.runoob.com???|???220?|?2016-05-16?| ????????????????|?Facebook?|?http://www.facebook.com?|???545?|?2016-05-16?| ????????????????|?cainiao??|?http://www.runoob.com???|???201?|?2016-05-17?| ????????????????+----------+-------------------------+-------+------------+ ?????* ?????*?【join】連接：用于把來自兩個或多個表的行結合起來?（笛卡兒積） ?????*?【INNER?JOIN】?關鍵字在表中存在至少一個匹配時返回行 ?????*?【LEFT?JOIN】?關鍵字從左表（table1）返回所有的行，即使右表（table2）中沒有匹配。如果右表中沒有匹配，則結果為?NULL。 ?????*?【RIGHT?JOIN】?關鍵字從右表（table2）返回所有的行，即使左表（table1）中沒有匹配。如果左表中沒有匹配，則結果為?NULL。 ?????*?【FULL?OUTER?JOIN】?關鍵字只要左表（table1）和右表（table2）其中一個表中存在匹配，則返回行. ?????*?【FULL?OUTER?JOIN】?關鍵字結合了?LEFT?JOIN?和?RIGHT?JOIN?的結果。 ?????*? ?????*??????【INNER?JOIN】 ?????*??????mysql>?select?website.id,website.name,website.alexa,website.country,access.aid,access.site_id,access.count ????????????????->?from?website?inner?join?access?on?website.id=access.site_id； ????????????????+------+----------+-------+---------+------+---------+-------+????????????????|?id???|?name?????|?alexa?|?country?|?aid??|?site_id?|?count?| ????????????????+------+----------+-------+---------+------+---------+-------+????????????????|????1?|?Google???|?????1?|?USA?????|????1?|???????1?|????45?| ????????????????|????3?|?cainiao??|???673?|?CN??????|????2?|???????3?|???100?| ????????????????|????1?|?Google???|?????1?|?USA?????|????3?|???????1?|???230?| ????????????????|????2?|?taobao???|????13?|?CN??????|????4?|???????2?|????10?| ????????????????|????5?|?Facebook?|?????3?|?USA?????|????5?|???????5?|???206?| ????????????????|????4?|?weibo????|????20?|?CN??????|????6?|???????4?|????13?| ????????????????|????3?|?cainiao??|???673?|?CN??????|????7?|???????3?|???220?| ????????????????|????5?|?Facebook?|?????3?|?USA?????|????8?|???????5?|???545?| ????????????????|????3?|?cainiao??|???673?|?CN??????|????9?|???????3?|???201?| ????????????????+------+----------+-------+---------+------+---------+-------+ ?????* ?????*??????【LEFT?JOIN】 ?????*??????mysql>?select?website.id,website.name,website.alexa,website.country,access.aid,access.site_id,access.count ????????????????->?from?website?left?join?access?on?website.id=access.site_id; ????????????????+------+----------+-------+---------+------+---------+-------+????????????????|?id???|?name?????|?alexa?|?country?|?aid??|?site_id?|?count?| ????????????????+------+----------+-------+---------+------+---------+-------+????????????????|????1?|?Google???|?????1?|?USA?????|????1?|???????1?|????45?| ????????????????|????1?|?Google???|?????1?|?USA?????|????3?|???????1?|???230?| ????????????????|????2?|?taobao???|????13?|?CN??????|????4?|???????2?|????10?| ????????????????|????3?|?cainiao??|???673?|?CN??????|????2?|???????3?|???100?| ????????????????|????3?|?cainiao??|???673?|?CN??????|????7?|???????3?|???220?| ????????????????|????3?|?cainiao??|???673?|?CN??????|????9?|???????3?|???201?| ????????????????|????4?|?weibo????|????20?|?CN??????|????6?|???????4?|????13?| ????????????????|????5?|?Facebook?|?????3?|?USA?????|????5?|???????5?|???206?| ????????????????|????5?|?Facebook?|?????3?|?USA?????|????8?|???????5?|???545?| ????????????????|????7?|?ali??????|????32?|?CN??????|?NULL?|????NULL?|??NULL?| ????????????????+------+----------+-------+---------+------+---------+-------+ ?????* ?????*??????mysql>?select?website.id,website.name,website.alexa,website.country,access.aid,access.site_id,access.count ????????????????->?from?website?left?join?access?on?website.alexa=access.aid; ????????????????+------+----------+-------+---------+------+---------+-------+????????????????|?id???|?name?????|?alexa?|?country?|?aid??|?site_id?|?count?| ????????????????+------+----------+-------+---------+------+---------+-------+????????????????|????1?|?Google???|?????1?|?USA?????|????1?|???????1?|????45?| ????????????????|????2?|?taobao???|????13?|?CN??????|?NULL?|????NULL?|??NULL?| ????????????????|????3?|?cainiao??|???673?|?CN??????|?NULL?|????NULL?|??NULL?| ????????????????|????4?|?weibo????|????20?|?CN??????|?NULL?|????NULL?|??NULL?| ????????????????|????5?|?Facebook?|?????3?|?USA?????|????3?|???????1?|???230?| ????????????????|????7?|?ali??????|????32?|?CN??????|?NULL?|????NULL?|??NULL?| ????????????????+------+----------+-------+---------+------+---------+-------+ ?????* ?????*??????【RIGHT?JOIN】 ?????*??????mysql>?select?website.id,website.name,website.alexa,website.country,access.aid,access.site_id,access.count ????????????????->?from?website?right?join?access?on?website.alexa=access.aid; ????????????????+------+----------+-------+---------+------+---------+-------+????????????????|?id???|?name?????|?alexa?|?country?|?aid??|?site_id?|?count?| ????????????????+------+----------+-------+---------+------+---------+-------+????????????????|????1?|?Google???|?????1?|?USA?????|????1?|???????1?|????45?| ????????????????|?NULL?|?NULL?????|??NULL?|?NULL????|????2?|???????3?|???100?| ????????????????|????5?|?Facebook?|?????3?|?USA?????|????3?|???????1?|???230?| ????????????????|?NULL?|?NULL?????|??NULL?|?NULL????|????4?|???????2?|????10?| ????????????????|?NULL?|?NULL?????|??NULL?|?NULL????|????5?|???????5?|???206?| ????????????????|?NULL?|?NULL?????|??NULL?|?NULL????|????6?|???????4?|????13?| ????????????????|?NULL?|?NULL?????|??NULL?|?NULL????|????7?|???????3?|???220?| ????????????????|?NULL?|?NULL?????|??NULL?|?NULL????|????8?|???????5?|???545?| ????????????????|?NULL?|?NULL?????|??NULL?|?NULL????|????9?|???????3?|???201?| ????????????????+------+----------+-------+---------+------+---------+-------+ ?????* ?????* ?????*【union】操作符：合并兩個或多個?SELECT?語句的結果 ?????*??????注意：UNION?內部的每個?SELECT?語句必須擁有相同數量的列。列也必須擁有相似的數據類型。 ?????*??????????????同時，每個?SELECT?語句中的列的順序必須相同。 ?????* ?????*??????注意：默認地，UNION?操作符選取不同的值。如果允許重復的值，請使用?UNION?ALL ?????* ?????*??????mysql>?select?country?from?app ????????????????->?union ????????????????->?select?country?from?website; ????????????????+---------+????????????????|?country?| ????????????????+---------+????????????????|?CN??????| ????????????????|?USA?????| ????????????????+---------+ ????????????mysql>?select?country?from?app ????????????????->?union?all ????????????????->?select?country?from?website; ????????????????+---------+????????????????|?country?| ????????????????+---------+????????????????|?CN??????| ????????????????|?CN??????| ????????????????|?CN??????| ????????????????|?USA?????| ????????????????|?CN??????| ????????????????|?CN??????| ????????????????|?CN??????| ????????????????|?USA?????| ????????????????|?CN??????| ????????????????+---------+ ?????* ?????* ?????*select?into:從一個表中復制數據，然后插入到一個新表中 ?????*insert?into?select:從一個表復制數據，然后把數據插入到一個已存在的表中 ?????*??????區別：?select?into?from?要求目標表不存在，因為在插入時會自動創建。 ?????*????????????insert?into?select?from?要求目標表存在，直接進行插入。 ?????*?????? ?????*??????【select?into】 ?????*?★★★★注意：mysql不支持select?into語句 ?????*???????????可以替換為：create?table?newtable(select?*?from?website); ?????*??????mysql>?create?table?newtable(select?*?from?website); ????????????????Query?OK,?6?rows?affected?(0.17?sec) ????????????????Records:?6??Duplicates:?0??Warnings:?0 ????????????mysql>?select?*?from?newtable; ????????????????+------+----------+-------------------------+-------+---------+????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????+------+----------+-------------------------+-------+---------+????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????| ????????????????+------+----------+-------------------------+-------+---------+ ?????* ?????*??????【insert?into?select】 ?????*??????mysql>?create?table?web(id?int,name?varchar(20),url?varchar(50),alexa?int,country?varchar(20)); ????????????????Query?OK,?0?rows?affected?(0.17?sec) ?????* ?????*??????mysql>?insert?into?web ????????????????->?select?*?from?website; ????????????????Query?OK,?6?rows?affected?(0.06?sec) ????????????????Records:?6??Duplicates:?0??Warnings:?0 ?????* ?????*??????mysql>?select?*?from?web; ????????????????+------+----------+-------------------------+-------+---------+????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????+------+----------+-------------------------+-------+---------+????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????| ????????????????+------+----------+-------------------------+-------+---------+ ?????* ?????*?【drop】:撤銷索引，撤銷表，撤銷數據庫 ?????*??????【drop?index】刪除表中的索引 ?????*??????drop?index?index_name?on?table_name;//MS?Access ?????*??????drop?index?table_name.index_name;//MS?SQL ?????*??????drop?index?index_name;//DB2/ORACLE ?????*??????alter?table?table_name?drop?index?index_name;//MySQL ?????* ?????*??????【drop?table】刪除表 ?????*??????drop?table?table_name; ?????* ?????*??????????mysql>?show?tables; ????????????????????+----------------+????????????????????|?Tables_in_test?| ????????????????????+----------------+????????????????????|?access?????????| ????????????????????|?app????????????| ????????????????????|?newtable???????| ????????????????????|?web????????????| ????????????????????|?website????????| ????????????????????|?websites???????| ????????????????????+----------------+ ????????????????mysql>?drop?table?newtable; ????????????????mysql>?show?tables; ????????????????????+----------------+????????????????????|?Tables_in_test?| ????????????????????+----------------+????????????????????|?access?????????| ????????????????????|?app????????????| ????????????????????|?web????????????| ????????????????????|?website????????| ????????????????????|?websites???????| ????????????????????+----------------+?? ?????* ?????*??????【drop?database】刪除數據庫 ?????*??????drop?database?database_name; ?????* ?????*??????????mysql>?show?databases; ????????????????????+--------------------+????????????????????|?Database???????????| ????????????????????+--------------------+????????????????????|?information_schema?| ????????????????????|?data1??????????????| ????????????????????|?data2??????????????| ????????????????????|?my_db??????????????| ????????????????????|?mysql??????????????| ????????????????????|?performance_schema?| ????????????????????|?test???????????????| ????????????????????+--------------------+ ????????????????mysql>?drop?database?my_db; ????????????????mysql>?show?databases; ????????????????????+--------------------+????????????????????|?Database???????????| ????????????????????+--------------------+????????????????????|?information_schema?| ????????????????????|?data1??????????????| ????????????????????|?data2??????????????| ????????????????????|?mysql??????????????| ????????????????????|?performance_schema?| ????????????????????|?test???????????????| ????????????????????+--------------------+ ?????*?????? ?????*??????【truncate?table】刪除表中的數據，但不刪除表本身 ?????*??????truncate?table?table_name; ?????* ?????*??????????mysql>?select?*?from?websites; ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????| ????????????????????+------+----------+-------------------------+-------+---------+ ????????????????mysql>?truncate?table?websites; ????????????????mysql>?select?*?from?websites; ????????????????????Empty?set?(0.00?sec) ?????*【alter?table】:在已有的表中添加、刪除或修改列? ?????*??????★★★★★★★ ?????*??????【添加列】： ?????*??????alter?table?table_name ?????*??????add?column_name?datatype; ?????* ?????*??????????mysql>?select?*?from?website; ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????| ????????????????????+------+----------+-------------------------+-------+---------+ ????????????????mysql>?alter?table?website ????????????????????->?add?date?date; ????????????????????Query?OK,?6?rows?affected?(0.35?sec) ????????????????????Records:?6??Duplicates:?0??Warnings:?0 ????????????????mysql>?select?*?from?website; ????????????????????+------+----------+-------------------------+-------+---------+------+????????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?|?date?| ????????????????????+------+----------+-------------------------+-------+---------+------+????????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????|?NULL?| ????????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????|?NULL?| ????????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????|?NULL?| ????????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????|?NULL?| ????????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????|?NULL?| ????????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????|?NULL?| ????????????????????+------+----------+-------------------------+-------+---------+------+ ?????*?????? ?????*??????【刪除列】： ?????*??????alter?table?table_name ?????*??????drop?column?column_name; ?????* ?????*??????????mysql>?alter?table?website ????????????????????->?drop?date; ????????????????????Query?OK,?6?rows?affected?(0.24?sec) ????????????????????Records:?6??Duplicates:?0??Warnings:?0 ????????????????mysql>?select?*?from?website; ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|?id???|?name?????|?url?????????????????????|?alexa?|?country?| ????????????????????+------+----------+-------------------------+-------+---------+????????????????????|????1?|?Google???|?http://www.google.com???|?????1?|?USA?????| ????????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????| ????????????????????+------+----------+-------------------------+-------+---------+ ?????*?????? ?????*??????【修改列】： ?????*??????【SQL/MS?Access】 ?????*??????alter?table?table_name ?????*??????alter?column?column_name?datatype; ?????*??????【MySQL/Oracle】 ?????*??????alter?table?table_name ?????*??????modify?column?column_name?datatype; ?????* ?????* ?????*【SQL約束】：用于規定表中的數據規則 ?????*??????如果存在違反約束的數據行為，行為會被約束終止。 ????????????約束可以在創建表時規定（通過?CREATE?TABLE?語句），或者在表創建之后規定（通過?ALTER?TABLE?語句）。 ?????* ?????*??在創建表的時候進行約束定義： ?????*??????create?table?table_name( ?????*??????column_name_1?data_type(size)?constaint_name; ?????*??????column_name_2?data-type(size)?constaint_name; ?????*??????column_name_3?data_type(size)?constaint_name; ?????*??????); ?????* ?????*??約束包括以下幾點： ?????*??????not?null:說明某列元素不能為空 ?????*??????unique:保證某列的每行必須有唯一的值 ?????*??????primary?key:?主鍵，not?null和unique的結合，保證實體完整性 ?????*??????foreign?key：外鍵，保證參照完整性 ?????*??????check：保證列中的值符合指定的條件 ?????*??????default：規定沒有給列賦值時的默認值 ?????* ?????*??????【not?null】 ?????*??????mysql>?create?table?persons(id?int?not?null,name?varchar(20),address?varchar(20),city?varchar(20)); ?????* ?????*??????mysql>?insert?into?persons ????????????????->?(name)?values?('mary'); ????????????????ERROR?1364?(HY000):?Field?'id'?doesn't?have?a?default?value?//必須給id賦值，id不能為空，約束條件為not?null ????????????mysql>?insert?into?persons ????????????????->?(id,name,address,city) ????????????????->?values?(1,'mary','xian','changan'); ????????????mysql>?select?*?from?persons; ????????????????+----+------+---------+---------+????????????????|?id?|?name?|?address?|?city????| ????????????????+----+------+---------+---------+????????????????|??1?|?mary?|?xian????|?changan?| ????????????????+----+------+---------+---------+ ?????*?????? ?????*??????【unique】 ?????*??????mysql>?create?table?person01(id?int?not?null,name?varchar(20)?unique,address?varchar(20),city?varchar(20)); ?????* ?????*??????mysql>?insert?into?person01?(id,name,address,city)?values?(1,'mary','xian','changan'); ?????* ?????*??????mysql>?insert?into?person01?(id,name,address,city)?values?(2,'mary','ningxia','yinchuan'); ????????????????ERROR?1062?(23000):?Duplicate?entry?'mary'?for?key?'name' ????????????mysql>?insert?into?person01?(id,name,address,city)?values?(1,'mary','ningxia','yinchuan'); ????????????????ERROR?1062?(23000):?Duplicate?entry?'mary'?for?key?'name' ????????????mysql>?insert?into?person01?(id,name,address,city)?values?(2,'Lily','ningxia','yinchuan'); ????????????????Query?OK,?1?row?affected?(0.03?sec) ?????*?? ?????*??MySQL:??????????????????????????????SQL?Server?/?Oracle?/?MS?Access?： ?????*??????CREATE?TABLE?Persons????????????????????????????????CREATE?TABLE?Persons ????????????(???????????????????????????????????????????????????( ????????????P_Id?int?NOT?NULL,??????????????????????????????????P_Id?int?NOT?NULL?UNIQUE, ????????????LastName?varchar(255)?NOT?NULL,?????????????????????LastName?varchar(255)?NOT?NULL, ????????????FirstName?varchar(255),?????????????????????????????FirstName?varchar(255), ????????????Address?varchar(255),???????????????????????????????Address?varchar(255), ????????????City?varchar(255),??????????????????????????????????City?varchar(255), ????????????UNIQUE?(P_Id)???????????????????????????????????????); ????????????); ?????*?? ?????*??如需命名?UNIQUE?約束，并定義多個列的?UNIQUE?約束，請使用下面的?SQL?語法: ?????*??????????MySQL?/?SQL?Server?/?Oracle?/?MS?Access： ?????*??????????????????CREATE?TABLE?Persons ????????????????????????( ????????????????????????P_Id?int?NOT?NULL, ????????????????????????LastName?varchar(255)?NOT?NULL, ????????????????????????FirstName?varchar(255), ????????????????????????Address?varchar(255), ????????????????????????City?varchar(255), ????????????????????????CONSTRAINT?uc_PersonID?UNIQUE?(P_Id,LastName) ????????????????????????);?? ?????*?????? ?????*??????撤銷unique： ?????*??????????alter?table?website ?????*??????????drop?index?id; ?????* ?????*??????【primary】主鍵，主鍵必須包含唯一的值，主鍵列不能包含null值，每個表都應該有一個主鍵，而且每個表只能有一個主鍵 ?????*?????????? ?????*??????MySQL:????????????????????????????????????SQL?Server?/?Oracle?/?MS?Access： ?????*??????????CREATE?TABLE?Persons????????????????????????????CREATE?TABLE?Persons???? ????????????????(???????????????????????????????????????????????( ????????????????P_Id?int?NOT?NULL,???????????????????????????????P_Id?int?NOT?NULL?PRIMARY?KEY, ????????????????LastName?varchar(255)?NOT?NULL,??????????????????LastName?varchar(255)?NOT?NULL, ????????????????FirstName?varchar(255),??????????????????????????FirstName?varchar(255), ????????????????Address?varchar(255),????????????????????????????Address?varchar(255), ????????????????City?varchar(255),???????????????????????????????City?varchar(255), ????????????????PRIMARY?KEY?(P_Id)???????????????????????????????); ????????????????); ?????*?????? ?????*??????當表已經創建了，再繼續添加主鍵primary?key:???????需命名?PRIMARY?KEY?約束，并定義多個列的?PRIMARY?KEY?約束，請使用下面的?SQL?語法： ?????*??????MySQL?/?SQL?Server?/?Oracle?/?MS?Access：???????????? ?????*??????????alter?table?website?????????????????????????????alter?table?website ?????*??????????add?primary?key(id);????????????????????????????add?constraint? ?????*?????? ?????*??????????mysql>?desc?person; ????????????????????+-----------+-------------+------+-----+---------+-------+????????????????????|?Field?????|?Type????????|?Null?|?Key?|?Default?|?Extra?| ????????????????????+-----------+-------------+------+-----+---------+-------+????????????????????|?id????????|?int(11)?????|?NO???|?????|?0???????|???????| ????????????????????|?LastName??|?varchar(10)?|?YES??|?????|?NULL????|???????| ????????????????????|?FirstName?|?varchar(10)?|?YES??|?????|?NULL????|???????| ????????????????????|?Address???|?varchar(50)?|?YES??|?????|?NULL????|???????| ????????????????????|?City??????|?varchar(20)?|?YES??|?????|?NULL????|???????| ????????????????????+-----------+-------------+------+-----+---------+-------+ ?????* ?????*??????????mysql>?alter?table?person ????????????????????->?add?primary?key?(id); ????????????????????Query?OK,?0?rows?affected?(0.22?sec) ?????* ?????*??????????mysql>?desc?person; ????????????????????+-----------+-------------+------+-----+---------+-------+????????????????????|?Field?????|?Type????????|?Null?|?Key?|?Default?|?Extra?| ????????????????????+-----------+-------------+------+-----+---------+-------+????????????????????|?id????????|?int(11)?????|?NO???|?PRI?|?0???????|???????| ????????????????????|?LastName??|?varchar(10)?|?YES??|?????|?NULL????|???????| ????????????????????|?FirstName?|?varchar(10)?|?YES??|?????|?NULL????|???????| ????????????????????|?Address???|?varchar(50)?|?YES??|?????|?NULL????|???????| ????????????????????|?City??????|?varchar(20)?|?YES??|?????|?NULL????|???????| ????????????????????+-----------+-------------+------+-----+---------+-------+ ?????* ?????*??????????mysql>?alter?table?person ????????????????????->?drop?primary?key; ????????????????????Query?OK,?3?rows?affected?(0.27?sec) ?????* ?????*??????????mysql>?desc?person; ????????????????????+-----------+-------------+------+-----+---------+-------+????????????????????|?Field?????|?Type????????|?Null?|?Key?|?Default?|?Extra?| ????????????????????+-----------+-------------+------+-----+---------+-------+????????????????????|?id????????|?int(11)?????|?NO???|?????|?0???????|???????| ????????????????????|?LastName??|?varchar(10)?|?YES??|?????|?NULL????|???????| ????????????????????|?FirstName?|?varchar(10)?|?YES??|?????|?NULL????|???????| ????????????????????|?Address???|?varchar(50)?|?YES??|?????|?NULL????|???????| ????????????????????|?City??????|?varchar(20)?|?YES??|?????|?NULL????|???????| ????????????????????+-----------+-------------+------+-----+---------+-------+ ?????* ?????*??????【foreign】:一個表中的foreign?key?指向另一個表中的primary?key ?????*??????MySQL：??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????SQL?Server?/?Oracle?/?MS?Access： ?????*??????????CREATE?TABLE?Orders?????????????????????????????????????????????CREATE?TABLE?Orders ????????????????(???????????????????????????????????????????????????????????????( ????????????????O_Id?int?NOT?NULL,???????????????????????????????????????????????O_Id?int?NOT?NULL?primary?key, ????????????????OrderNo?int?NOT?NULL,????????????????????????????????????????????OrderNo?int?NOT?NULL, ????????????????P_Id?int,????????????????????????????????????????????????????????P_Id?int?foreign?key?references?Persons(P_Id) ????????????????PRIMARY?KEY?(O_Id),??????????????????????????????????????????????); ????????????????FOREIGN?KEY?(P_Id)?REFERENCES?Persons(P_Id) ????????????????); ?????*?????? ?????*??????當?"Orders"?表已被創建時，如需在?"P_Id"?列創建?FOREIGN?KEY?約束，請使用下面的?SQL： ?????*??????MySQL?/?SQL?Server?/?Oracle?/?MS?Access：??????????????????????????????????????????????MySQL?/?SQL?Server?/?Oracle?/?MS?Access：? ?????*??????????ALTER?TABLE?Orders???????????????????????????????????????????ALTER?TABLE?Orders ????????????????ADD?FOREIGN?KEY?(P_Id)???????????????????????????????????????ADD?FOREIGN?fk_PerOrders ????????????????REFERENCES?Persons(P_Id)?????????????????????????????????????FOREIGN?KEY?(P_Id)? ?????????????????????????????????????????????????????????????????????????????REFERENCES?Persons(P_Id) ?????*?????? ?????*??????撤銷foreign?key約束條件： ?????*??????MySQL:?????????????????????????????????????????????????????SQL?Server?/?Oracle?/?MS?Access： ?????*??????????ALTER?TABLE?Orders????????????????????????????????????????ALTER?TABLE?Orders ????????????????DROP?FOREIGN?KEY?fk_PerOrders?????????????????????????????DROP?constraint?KEY?fk_PerOrders ?????* ?????*??????【check】:用于限制列中值的范圍 ?????*??????????如果對單個列定義check約束，那么該列只允許特定的值 ?????*??????????如果對一個表定義check約束，那么詞約束會基于行中其他列的值在特定的列中隊值進行限制 ?????*??????MySQL：????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????SQL?Server?/?Oracle?/?MS?Access： ?????*??????????CREATE?TABLE?Persons????????????????????????????????????????CREATE?TABLE?Persons?? ????????????????(???????????????????????????????????????????????????????????( ????????????????P_Id?int?NOT?NULL,???????????????????????????????????????????P_Id?int?NOT?NULL?CHECK?(P_Id>0),?? ????????????????LastName?varchar(255)?NOT?NULL,??????????????????????????????LastName?varchar(255)?NOT?NULL,????? ????????????????FirstName?varchar(255),??????????????????????????????????????FirstName?varchar(255),??? ????????????????Address?varchar(255),????????????????????????????????????????Address?varchar(255),???? ????????????????City?varchar(255),???????????????????????????????????????????City?varchar(255),????????? ????????????????CHECK?(P_Id>0)???????????????????????????????????????????????);???????? ????????????????);???????????????????????????????????????????????????????????? ?????*?????? ?????*??????需命名?CHECK?約束，并定義多個列的?CHECK?約束，請使用下面的?SQL?語法： ?????*??????????MySQL?/?SQL?Server?/?Oracle?/?MS?Access： ?????*??????????????CREATE?TABLE?Persons ????????????????????( ????????????????????P_Id?int?NOT?NULL, ????????????????????LastName?varchar(255)?NOT?NULL, ????????????????????FirstName?varchar(255), ????????????????????Address?varchar(255), ????????????????????City?varchar(255), ????????????????????CONSTRAINT?chk_Person?CHECK?(P_Id>0?AND?City='Sandnes') ????????????????????) ?????* ?????*??????當表已被創建時，如需在?"P_Id"?列創建?CHECK?約束，請使用下面的?SQL： ?????*??????MySQL?/?SQL?Server?/?Oracle?/?MS?Access: ?????*??????????ALTER?TABLE?Persons ????????????????ADD?CHECK?(P_Id>0) ?????*??????如需命名?CHECK?約束，并定義多個列的?CHECK?約束，請使用下面的?SQL?語法： ?????*??????MySQL?/?SQL?Server?/?Oracle?/?MS?Access： ?????*??????????ALTER?TABLE?Persons ????????????????ADD?CONSTRAINT?chk_Person?CHECK?(P_Id>0?AND?City='Sandnes') ?????* ?????*??????撤銷?CHECK?約束： ?????*??????????SQL?Server?/?Oracle?/?MS?Access：????????????????????????????????????????????????????????? ?????MySQL： ?????*??????????????ALTER?TABLE?Persons??????????????????????????????????ALTER?TABLE?Persons ????????????????????DROP?CONSTRAINT?chk_Person???????????????????????????DROP?CHECK?chk_Person ?????* ?????*??????【default】:用于向列中插入默認值 ?????*??????My?SQL?/?SQL?Server?/?Oracle?/?MS?Access：???????????????????????????????????????????? ?????通過使用類似?GETDATE()?這樣的函數，DEFAULT?約束也可以用于插入系統值： ?????*??????????CREATE?TABLE?Persons?????????????????????????????????????????CREATE?TABLE?Orders?????????? ????????????????(????????????????????????????????????????????????????????????( ????????????????P_Id?int?NOT?NULL,????????????????????????????????????????????O_Id?int?NOT?NULL, ????????????????LastName?varchar(255)?NOT?NULL,???????????????????????????????OrderNo?int?NOT?NULL, ????????????????FirstName?varchar(255),???????????????????????????????????????P_Id?int, ????????????????Address?varchar(255),???????????????????????????????????OrderDate?date?DEFAULT?GETDATE() ????????????????City?varchar(255)?DEFAULT?'Sandnes'???????????????????????????) ????????????????) ?????* ?????*??????mysql>?create?table?person01(id?int,name?varchar(20),address?varchar(20),city?varchar(20)?default?'shanghai'); ?????* ?????*??????mysql>?insert?into?person01?(id,name,address)?values?(1,'Lily','xian'); ?????* ?????*??????mysql>?select?*?from?person01;//city被默認設置為shanghai ????????????????+------+------+---------+----------+????????????????|?id???|?name?|?address?|?city?????| ????????????????+------+------+---------+----------+????????????????|????1?|?Lily?|?xian????|?shanghai?| ????????????????+------+------+---------+----------+ ?????* ?????*??????當表已被創建時，如需在?"City"?列創建?DEFAULT?約束，請使用下面的?SQL： ?????*??????MySQL：???????????????????????????????????????????????????SQL?Server?/?MS?Access：????????????????????????????????????????????????????????????Oracle： ?????*??????????ALTER?TABLE?Persons??????????????????????ALTER?TABLE?Persons?????ALTER?TABLE?Persons ????????????????ALTER?City?SET?DEFAULT?'SANDNES'?????????ALTER?COLUMN?City?SET?DEFAULT?'SANDNES'MODIFY?City?DEFAULT?'SANDNES' ?????* ?????*??????撤銷?DEFAULT?約束： ?????*??????MySQL：?????????????????????????????SQL?Server?/?Oracle?/?MS?Access： ?????*??????????ALTER?TABLE?Persons????????????????????ALTER?TABLE?Persons ????????????????ALTER?City?DROP?DEFAULT????????????????ALTER?COLUMN?City?DROP?DEFAULT ?????* ?????*??????mysql>?alter?table?person01 ????????????????->?alter?date?set?default?'2016-3-2'; ????????????mysql>?select?*?from?person01; ????????????????+------+------+---------+----------+------------+????????????|?id???|?name?|?address?|?city??|?date?| ????????????????+------+------+---------+----------+------------+????????????|??1?|?Lily?|?xian?|?shanghai?|?NULL| ????????????????|????2?|?Mary?|?beijing?|?shanghai?|?2016-03-02?| ????????????????+------+------+---------+----------+------------+ ?????* ?????*【create?index】:用于在表中創建索引 ?????*??????????????????????????????????在不讀取整個表的情況下，索引使數據庫應用程序可以更快地查找數據。 ?????*????????????索引：可以在表中創建索引，以便更加快速高效的查詢數據 ?????*??????????????????用戶無法看到索引，它們只能被用來加快搜索/查詢 ?????*????????????注意：更新一個包含索引的表需要比更新一個沒有索引的表花費更多的時間，這是由于索引本身也需要更新。 ?????*??????????????????因此，理想的做法是僅僅在常常被索引的列上面創建索引。 ?????*???????????? ?????*?????在表上創建一個簡單的索引。允許使用重復的值：???????????????????????在表上創建一個唯一的索引。不允許使用重復的值： ?????*??????????CREATE?INDEX?index_name??????????????????????唯一的索引意味著兩個行不能擁有相同的索引值。 ????????????????ON?table_name?(column_name)????????????????????CREATE?UNIQUE?INDEX?index_name ?????*?????????????????????????????????????????????????????????ON?table_name?(column_name) ?????* ?????* ?????*【auto-increment】:會在新紀錄插入表中時生成一個唯一的數字 ?????*????????????????????????????????????????每次插入新記錄時，自動地創建主鍵字段的值 ?????* ?????*??SQL?語句把?"Persons"?表中的?"ID"?列定義為?auto-increment?主鍵字段 ?????*??????????CREATE?TABLE?Persons ????????????????( ????????????????ID?int?NOT?NULL?AUTO_INCREMENT, ????????????????LastName?varchar(255)?NOT?NULL, ????????????????FirstName?varchar(255), ????????????????Address?varchar(255), ????????????????City?varchar(255), ????????????????PRIMARY?KEY?(ID) ????????????????) ?????* ?????*??????mysql>?create?table?person03(id?int?not?null?AUTO_INCREMENT,name?varchar(20),primary?key(id)); ????????????????Query?OK,?0?rows?affected?(0.10?sec) ?????*??????注意：為屬性設置auto-increment時，必須是設置主鍵，自增是針對于主鍵而言的。 ?????*??????mysql>?insert?into?person03?(name)?value?('lily'); ?????*??????mysql>?insert?into?person03?(name)?value?('mary'); ?????*??????mysql>?insert?into?person03?(name)?value?('gass'); ?????* ?????*??????mysql>?select?*?from?person03; ????????????????+----+------+????????????????|?id?|?name?| ????????????????+----+------+????????????????|??1?|?lily?| ????????????????|??2?|?mary?| ????????????????|??3?|?gass?| ????????????????+----+------+ ?????* ?????*【views】視圖：視圖是可視化的表 ?????*??????????????創建、更新和刪除視圖 ?????*??????注釋：視圖總是顯示最新的數據！每當用戶查詢視圖時，數據庫引擎通過使用視圖的?SQL?語句重建數據。 ?????*?? ?????*??創建視圖：??? ?????*??????CREATE?VIEW?view_name?AS ????????????SELECT?column_name(s) ????????????FROM?table_name ????????????WHERE?condition ?????* ?????*??更新視圖： ?????*??????CREATE?OR?REPLACE?VIEW?view_name?AS ????????????SELECT?column_name(s) ????????????FROM?table_name ????????????WHERE?condition ?????* ?????*??撤銷視圖： ?????*??????DROP?VIEW?view_name ?????* ?????*【date】日期函數： ?????*??????NOW()?????????????????????????返回當前的日期和時間 ?????*??????CURDATE()??????????????返回當前的日期 ?????*??????CURTIME()??????????????返回當前的時間 ?????*??????DATE()????????????????????????提取日期或日期/時間表達式的日期部分 ?????*??????EXTRACT()??????????????返回日期/時間的單獨部分 ?????*??????DATE_ADD()?????????????向日期添加指定的時間間隔 ?????*??????DATE_SUB()?????????????從日期減去指定的時間間隔 ?????*??????DATEDIFF()?????????????返回兩個日期之間的天數 ?????*??????DATE_FORMAT()???用不同的格式顯示日期/時間 ?????* ?????*??mysql>?select?now(); ????????????+---------------------+????????????|?now()???????????????| ????????????+---------------------+????????????|?2016-07-14?14:49:07?| ????????????+---------------------+ ????????mysql>?select?curdate(); ????????????+------------+????????????|?curdate()??| ????????????+------------+????????????|?2016-07-14?| ????????????+------------+ ????????mysql>?select?curtime(); ????????????+-----------+????????????|?curtime()?| ????????????+-----------+????????????|?14:49:53??| ????????????+-----------+ ?????* ?????*【null】: ?????*??????IS?NULL: ?????*??????????SELECT?LastName,FirstName,Address?FROM?Persons ????????????????WHERE?Address?IS?NULL??? ?????* ?????*??????IS?NOT?NULL: ?????*??????????SELECT?LastName,FirstName,Address?FROM?Persons ????????????????WHERE?Address?IS?NOT?NULL ?????* ?????*【SQL?ISNULL()、NVL()、IFNULL()?和?COALESCE()?函數】：都是判斷表中是否為null,若為null，則返回1，若不空，則返回0 ?????*??????注意：在不同的數據庫中，使用不同的函數 ?????*??????SQL?Server?/?MS?Access：isnull() ?????*??????Oracle：nvl() ?????*??????MySQL：ifnull()/coalesce() ?????* ?????*??????mysql>?select?*?from?cal; ????????????????+----+------+-------+--------+------+????????????????|?id?|?name?|?first?|?second?|?sum??| ????????????????+----+------+-------+--------+------+????????????????|??1?|?lily?|????42?|??????3?|?NULL?| ????????????????+----+------+-------+--------+------+ ?????* ?????*??????mysql>?select?(first+second+isnull(sum))?as?s?from?cal; ????????????????+------+????????????????|?s????| ????????????????+------+????????????????|???46?| ????????????????+------+ ?????* ?????*??????mysql>?select?*?from?cal; ????????????????+----+------+-------+--------+------+????????????????|?id?|?name?|?first?|?second?|?sum??| ????????????????+----+------+-------+--------+------+????????????????|??1?|?lily?|????42?|??????3?|?NULL?| ????????????????|??2?|?mary?|????22?|????637?|?NULL?| ????????????????|??3?|?may??|????32?|?????43?|???75?| ????????????????+----+------+-------+--------+------+ ?????* ?????*??????mysql>?select?(first+second+!isnull(sum))?as?s?from?cal; ????????????????+------+????????????????|?s????| ????????????????+------+????????????????|???45?| ????????????????|??659?| ????????????????|???76?| ????????????????+------+ ?????* ?????*??????mysql>?select?(first+second+isnull(sum))?as?s?from?cal; ????????????????+------+????????????????|?s????| ????????????????+------+????????????????|???46?| ????????????????|??660?| ????????????????|???75?| ????????????????+------+ ?????*?????? ?????* ?????*-------------------------------------------------MySQL函數--------------------------------------------------- ?????* ?????*SQL?aggregate函數： ?????* ?????*??????avg():返回平均值 ?????*??????????mysql>?select?*?from?website; ????????????????????+------+----------+-------------------------+-------+---------+??????|?id?|?name?|?url|?alexa?|?country?| ????????????????????+------+----------+-------------------------+-------+---------+??|??1?|?Google|?http://www.google.com?|1?|?USA| ????????????????????|????2?|?taobao???|?http://www.taobao.com???|????13?|?CN??????| ????????????????????|????3?|?cainiao??|?http://www.runoob.com???|???673?|?CN??????| ????????????????????|????4?|?weibo????|?http://weibo.com????????|????20?|?CN??????| ????????????????????|????5?|?Facebook?|?http://www.facebook.com?|?????3?|?USA?????| ????????????????????|????7?|?ali??????|?http://www.ali.com??????|????32?|?CN??????| ????????????????????+------+----------+-------------------------+-------+---------+ ????????????????mysql>?select?avg(alexa)?as?avg_alexa ????????????????????->?from?website; ????????????????????+-----------+????????????????????|?avg_alexa?| ????????????????????+-----------+????????????????????|??123.6667?| ????????????????????+-----------+ ?????* ?????*??????count():返回數目 ?????*??????????mysql>?select?count(id)?as?count ????????????????????->?from?website; ????????????????????+-------+????????????????????|?count?| ????????????????????+-------+????????????????????|?????6?| ????????????????????+-------+ ?????* ?????*??????first():返回第一個記錄的值????//注釋：只有?MS?Access?支持?FIRST()函數 ?????*?????????? ?????*??????last():返回最后一個記錄的值?//注釋：只有?MS?Access?支持?LAST()?函數 ?????* ?????*??????max():返回最大值 ?????*??????????mysql>?select?max(id)?as?max ????????????????????->?from?website; ????????????????????+------+????????????????????|?max??| ????????????????????+------+????????????????????|????7?| ????????????????????+------+ ????????????????mysql>?select?max(id)?as?max,name,url,alexa,country ????????????????????->?from?website; ????????????????????+------+--------+-----------------------+-------+---------+?????|?max??|?name???|?url|?alexa?|?country?| ????????????????????+------+--------+-----------------------+-------+---------+???|??7?|?Google?|?http://www.google.com?|1?|?USA| ????????????????????+------+--------+-----------------------+-------+---------+ ?????*?????? ?????*??????min():返回最小值 ?????*??????????mysql>?select?min(id)?as?min ????????????????????->?from?website; ????????????????????+------+????????????????????|?min??| ????????????????????+------+????????????????????|????1?| ????????????????????+------+ ?????*?????? ?????*??????sum():返回總和 ?????*??????????mysql>?select?sum(alexa)?as?sum_alexa ????????????????????->?from?website; ????????????????????+-----------+????????????????????|?sum_alexa?| ????????????????????+-----------+????????????????????|???????742?| ????????????????????+-----------+ ?????* ?????* ?????*SQL?scalar函數： ?????*??????ucase():大寫轉換 ?????*??????????mysql>?select?id,ucase(name),url,alexa,country ????????????????????->?from?website; ????????????????????+------+-------------+-------------------------+-------+---------+?|?id?|?ucase(name)?|?url|?alexa?|?country?| ????????????????????+------+-------------+-------------------------+-------+---------+?|1?|?GOOGLE|?http://www.google.com?|?1?|?USA| ????????????????????|????2?|?TAOBAO??????|?http://www.taobao.com???|????13?|?CN?????? ????????????????????|????3?|?CAINIAO?????|?http://www.runoob.com???|???673?|?CN??????| ????????????????????|????4?|?WEIBO???????|?http://weibo.com????????|????20?|?CN??????| ????????????????????|????5?|?FACEBOOK????|?http://www.facebook.com?|?????3?|?USA?????| ????????????????????|????7?|?ALI?????????|?http://www.ali.com??????|????32?|?CN??????| ????????????????????+------+-------------+-------------------------+-------+---------+ ?????*?????? ?????*??????lcsse():小寫轉換 ?????*??????????mysql>?select?id,lcase(name),url,alexa,lcase(country) ????????????????????->?from?website; ????????????????????+------+-------------+-------------------------+-------+----------------+|?id|?lcase(name)|?url|?alexa|?lcase(country)| ????????????????????+------+-------------+-------------------------+-------+----------------+?|1?|?google|?http://www.google.com?|?1?|usa| ????????????????????|????2?|?taobao??????|?http://www.taobao.com???|????13?|?cn?????????????| ????????????????????|????3?|?cainiao?????|?http://www.runoob.com???|???673?|?cn?????????????| ????????????????????|????4?|?weibo???????|?http://weibo.com????????|????20?|?cn?????????????| ????????????????????|????5?|?facebook????|?http://www.facebook.com?|?????3?|?usa????????????| ????????????????????|????7?|?ali?????????|?http://www.ali.com??????|????32?|?cn?????????????| ????????????????????+------+-------------+-------------------------+-------+----------------+ ?????*?????? ?????*??????mid():從文本中提取字符?????格式：mid(column_name,start,length) ?????*??????????mysql>?select?mid(name,1,4)?as?mid ????????????????????->?from?website; ????????????????????+------+????????????????????|?mid??| ????????????????????+------+????????????????????|?Goog?| ????????????????????|?taob?| ????????????????????|?cain?| ????????????????????|?weib?| ????????????????????|?Face?| ????????????????????|?ali??| ????????????????????+------+ ?????*?????? ?????*??????len():返回長度???格式：length(column) ?????*??????????mysql>?select?id,name,length(url),alexa,country ????????????????????->?from?website; ????????????????????+------+----------+-------------+-------+---------+??????|?id???|?name?|?length(url)?|?alexa?|?country?| ????????????????????+------+----------+-------------+-------+---------+??????|????1?|?Google???|??21?|?1?|?USA?| ????????????????????|????2?|?taobao???|??????????21?|????13?|?CN??????| ????????????????????|????3?|?cainiao??|??????????21?|???673?|?CN??????| ????????????????????|????4?|?weibo????|??????????16?|????20?|?CN??????| ????????????????????|????5?|?Facebook?|??????????23?|?????3?|?USA?????| ????????????????????|????7?|?ali??????|??????????18?|????32?|?CN??????| ????????????????????+------+----------+-------------+-------+---------+ ?????*?????? ?????*??????round():指定小數的四舍五入????格式：SELECT?ROUND(column_name,decimals)?FROM?table_name; ?????*??????????mysql>?select?round(1.3234); ????????????????????+---------------+????????????????????|?round(1.3234)?| ????????????????????+---------------+????????????????????|?????????????1?| ????????????????????+---------------+ ????????????????mysql>?select?round(23.43434,3); ????????????????????+-------------------+????????????????????|?round(23.43434,3)?| ????????????????????+-------------------+????????????????????|????????????23.434?| ????????????????????+-------------------+ ?????*?????? ?????*??????now():返回當前的系統日期和時間????格式：SELECT?NOW()?FROM?table_name; ?????*??????????mysql>?select?now(); ????????????????????+---------------------+????????????????????|?now()???????????????| ????????????????????+---------------------+????????????????????|?2016-07-13?22:56:04?| ????????????????????+---------------------+????????????????????????? ?????*?????? ?????*??????mysql>?select?id,name,url,now()?as?date ????????????????->?from?website; ????????????????????+------+----------+-------------------------+---------------------+????????|?id??|?name??|?url?|?date?| ????????????????????+------+----------+-------------------------+---------------------+?|??1|?Google?|???|?2016-07-13?22:57:30?| ????????????????????|????2?|?taobao???|?http://www.taobao.com???|?2016-07-13?22:57:30?| ????????????????????|????3?|?cainiao??|?http://www.runoob.com???|?2016-07-13?22:57:30?| ????????????????????|????4?|?weibo????|?http://weibo.com????????|?2016-07-13?22:57:30?| ????????????????????|????5?|?Facebook?|?http://www.facebook.com?|?2016-07-13?22:57:30?| ????????????????????|????7?|?ali??????|?http://www.ali.com??????|?2016-07-13?22:57:30?| ????????????????????+------+----------+-------------------------+---------------------+? ?????* ?????*??????format():格式化某個字段的顯示方式????格式：SELECT?FORMAT(column_name,format)?FROM?table_name; ?????* ?????* ?????*??????group?by:用于結合聚合函數，根據一個或多個列對結果進行分組 ?????*??????????SELECT?column_name,?aggregate_function(column_name) ????????????????FROM?table_name ????????????????WHERE?column_name?operator?value ????????????????GROUP?BY?column_name; ?????* ?????*??????????mysql>?select?site_id,?sum(count)?as?sum ????????????????????->?from?access ????????????????????->?group?by?site_id; ????????????????????+---------+------+????????????????????|?site_id?|?sum??| ????????????????????+---------+------+????????????????????|???????1?|??275?| ????????????????????|???????2?|???10?| ????????????????????|???????3?|??521?| ????????????????????|???????4?|???13?| ????????????????????|???????5?|??751?| ????????????????????+---------+------+ ?????* ?????* ?????*??????having子句：在?SQL?中增加?HAVING?子句原因是，WHERE?關鍵字無法與聚合函數一起使用。 ????????????????????????HAVING?子句可以讓我們篩選分組后的各組數據。 ?????*??????????SELECT?column_name,?aggregate_function(column_name) ????????????????FROM?table_name ????????????????WHERE?column_name?operator?value ????????????????GROUP?BY?column_name ????????????????HAVING?aggregate_function(column_name)?operator?value; ?????* ?????*??????mysql>?select?site_id,sum(count) ????????????????->?from?access ????????????????->?group?by?site_id ????????????????->?having?sum(count)>100; ????????????????+---------+------------+????????????????|?site_id?|?sum(count)?| ????????????????+---------+------------+????????????????|???????1?|????????275?| ????????????????|???????3?|????????521?| ????????????????|???????5?|????????751?| ????????????????+---------+------------+ ?????* ?????*?*/ ????????System.out.println("10h?over"); ????????System.out.println("終于敲完了！"); ????} }
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