经典SQL语句大全（3）

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 '+ @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�]有及格的成�，在每次增�L0.1的基�A上，使他����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