精妙SQL语句收集(转)
- SQL语句先前写的时候,很容易把一些特殊的用法忘记,我特此整理了一下SQL语句操作。
- 一、基础
- 1、说明:创建数据库
- CREATE DATABASE database-name
- 2、说明:删除数据库
- drop database dbname
- 3、说明: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
- 4、说明: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:create table tab_new like tab_old (使用旧表创建新表)
- B:create table tab_new as select col1,col2… from tab_old definition only
- 5、说明:删除新表
- drop table tabname
- 6、说明:增加一个列
- Alter table tabname add column col type
- 注:列增加后将不能删除。DB2中列加上后数据类型也不能改变,唯一能改变的是增加varchar类型的长度。
- 7、说明:添加主键: Alter table tabname add primary key(col)
- 说明:删除主键: Alter table tabname drop primary key(col)
- 8、说明:创建索引:create [unique] index idxname on tabname(col….)
- 删除索引:drop index idxname
- 注:索引是不可更改的,想更改必须删除重新建。
- 9、说明:创建视图:create view viewname as select statement
- 删除视图:drop view viewname
- 10、说明:几个简单的基本的sql语句
- 选择:select * from table1 where 范围
- 插入:insert into table1(field1,field2) values(value1,value2)
- 删除:delete from table1 where 范围
- 更新:update table1 set field1=value1 where 范围
- 查找:select * from table1 where field1 like ‘%value1%’ —like的语法很精妙,查资料!
- 排序:select * from table1 order by field1,field2 [desc]
- 总数:select count as totalcount from table1
- 求和:select sum(field1) as sumvalue from table1
- 平均:select avg(field1) as avgvalue from table1
- 最大:select max(field1) as maxvalue from table1
- 最小:select min(field1) as minvalue from table1
- 11、说明: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。
- 12、说明:使用外连接
- A、left outer join:
- 左外连接(左连接):结果集几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。
- 二、提升
- 1、说明: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
- 2、说明: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 b;
- 3、说明: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 b in ‘具体数据库’ where 条件
- 例子:..from b in ‘”&Server.MapPath(“.”)&”/data.mdb” &”‘ where..
- 4、说明: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)
- 5、说明: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
- 6、说明: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
- 7、说明:在线视图查询(表名1:a )
- select * from (SELECT a,b,c FROM a) T where t.a > 1;
- 8、说明: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
- 9、说明:in 的使用方法
- select * from table1 where a [not] in (‘值1′,’值2′,’值4′,’值6’)
- 10、说明:两张关联表,删除主表中已经在副表中没有的信息
- delete from table1 where not exists ( select * from table2 where table1.field1=table2.field1 )
- 11、说明: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 …..
- 12、说明: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
- 13、说明: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
- 14、说明:前10条记录
- select top 10 * form table1 where 范围
- 15、说明: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)
- 16、说明: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)
- 17、说明:随机取出10条数据
- select top 10 * from tablename order by newid()
- 18、说明:随机选择记录
- select newid()
- 19、说明:删除重复记录
- Delete from tablename where id not in (select max(id) from tablename group by col1,col2,…)
- 20、说明:列出数据库里所有的表名
- select name from sysobjects where type=‘U’
- 21、说明:列出表里的所有的
- select name from syscolumns where id=object_id(‘TableName’)
- 22、说明: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
- 23、说明:初始化表table1
- TRUNCATE TABLE table1
- 24、说明:选择从10到15的记录
- select top 5 * from (select top 15 * from table order by id asc) table_别名 order by id desc
- 三、技巧
- 1、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 安定 ‘+ @strWhere
- 2、收缩数据库
- –重建索引
- DBCC REINDEX
- DBCC INDEXDEFRAG
- –收缩数据和日志
- DBCC SHRINKDB
- DBCC SHRINKFILE
- 3、压缩数据库
- dbcc shrinkdatabase(dbname)
- 4、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
- 5、检查备份集
- RESTORE VERIFYONLY from disk=‘E:/dvbbs.bak’
- 6、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
- 7、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
- 8、说明:更改某个表
- exec sp_changeobjectowner ‘tablename’,’dbo’
- 9、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
- 10、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)
我们不是制造者,我们是代码搬运工