经典SQL语句大全之（基础，提升，技巧）(四)

三、技巧

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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 !='' beginset @strSQL = 'select count(*) as Total from [' + @tblName + '] where ' + @strWhere endelse beginset @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 REINDEXDBCC INDEXDEFRAG--收缩数据和日志DBCC SHRINKDBDBCC SHRINKFILE

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3、压缩数据库dbcc shrinkdatabase(dbname)

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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

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5、检查备份集RESTORE VERIFYONLY from disk='E:\dvbbs.bak'

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6、修复数据库ALTER DATABASE [dvbbs] SET SINGLE_USERGODBCC CHECKDB('dvbbs',repair_allow_data_loss) WITH TABLOCKGOALTER DATABASE [dvbbs] SET MULTI_USERGO

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7、日志清除SET NOCOUNT ONDECLARE @LogicalFileName sysname, @MaxMinutes INT, @NewSize INT

USE tablename

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-- 要操作的数据库名SELECT @LogicalFileName = 'tablename_log',

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-- 日志文件名@MaxMinutes = 10, -- Limit on time allowed to wrap log. @NewSize = 1

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-- 你想设定的日志文件的大小(M)

Setup / initializeDECLARE @OriginalSize intSELECT @OriginalSize = size FROM sysfiles WHERE name = @LogicalFileNameSELECT '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 = @LogicalFileNameCREATE TABLE DummyTrans (DummyColumn char (8000) not null) www.2cto.com

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) ENDSELECT '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 = @LogicalFileNameDROP TABLE DummyTransSET NOCOUNT OFF

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8、说明：更改某个表exec sp_changeobjectowner 'tablename','dbo'

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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 sysobjectswhere user_name(uid)=@OldOwnerorder by name

OPEN curObjectFETCH NEXT FROM curObject INTO @Name, @OwnerWHILE(@@FETCH_STATUS=0)BEGIN if @Owner=@OldOwner begin set @OwnerName = @OldOwner + '.' + rtrim(@Name) exec sp_changeobjectowner @OwnerName, @NewOwnerend-- select @name,@NewOwner,@OldOwner

FETCH NEXT FROM curObject INTO @Name, @OwnerEND

close curObjectdeallocate curObjectGO

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10、SQL SERVER中直接循环写入数据declare @i intset @i=1while @i<30begin insert into test (userid) values(@i) set @i=@i+1end案例：有如下表，要求就裱中所有 有及格的成 ，在每次增 0.1的基 上，使他 好及格:

Name score www.2cto.com

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

作者 OPK62