SQL语句大全--<技巧>

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

错误！未找到目录项。
set @strSQL = ''select count(*) as Total from ['' + @tblName + ''] where 1=1安定''+ @strWhere2、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:

Namescore

Zhangshan80

Lishi59

Wangwu50

Songquan69

while((selectmin(score) from tb_table)<60)

begin

update tb_table set score=score*1.01

where score<60

if(selectmin(score) from tb_table)>60

break

else

continue

end