经典SQL语句大全(技巧)三

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


错误！未找到目录项。


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

案例


：



有如下表，要求就裱中所有沒有及格的成績，在每次增長0.1
的基礎上，使他們剛好及格:




Name
score


Zhangshan

80


Lishi

59


Wangwu

50


Songquan

69

while((select


min

(score) from tb_table)<

60

)


begin


update
tb_table set score

=

score*

1.01


where score

<60


if
(select

min

(score)
from tb_table)

>60



break



else



continue


end