SQL教程(三)

SQL经典语句大全(j技巧篇),SQL教程,技巧篇sql语句


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


Zhangshan80


Lishi       59


Wangwu      50


Songquan69


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





注:由于是很久之前整理的,如果使用时出现错误,请及时联系更改。谢谢。

  • 发表于 2017-11-16 10:32
  • 阅读 ( 1715 )
  • 分类:database

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