数据库

经典SQL语句大全之技巧篇

2011-04-15

 

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

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

可以直接写成

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:\3652s.bak

6、修复数据库

ALTER DATABASE [3652s] SET SINGLE_USER
GO
DBCC CHECKDB( 3652s ,repair_allow_data_loss) WITH TABLOCK
GO
ALTER DATABASE [3652s] 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、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

如:在下表中,要求就表中所有没有及格的成绩,在每次增长0.1的基础上,使他们刚好及格:

    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