精妙SQL速查 - [数据库]
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 


select type,vender,amount=sum( 

case vender 

when 'A' then pcs 

when 'B' then pcs 

when 'C' then pcs 

else 0 

end) 

FROM salary  

group by type,vender 





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 


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)