MySQL教程之技巧
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
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
dbcc shrinkdatabase(dbname)
exec sp_change_users_login ‘update_one’,’newname’,’oldname’
go
RESTORE VERIFYONLY from disk=’E:\dvbbs.bak’
ALTER DATABASE [dvbbs] SET SINGLE_USER
GO
DBCC CHECKDB(‘dvbbs’,repair_allow_data_loss) WITH TABLOCK
GO
ALTER DATABASE [dvbbs] SET MULTI_USER
GO
SET NOCOUNT ON
DECLARE @LogicalFileName sysname,
@MaxMinutes INT,
@NewSize INT
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)
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)
@StartTime DATETIME,
@TruncLog VARCHAR(255)
SELECT @StartTime = GETDATE(),
@TruncLog = ‘BACKUP LOG ‘ + db_name() + ‘ WITH TRUNCATE_ONLY’
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
exec sp_changeobjectowner ‘tablename’,’dbo’
@OldOwner as NVARCHAR(128),
@NewOwner as NVARCHAR(128)
AS
DECLARE @Owner as NVARCHAR(128)
DECLARE @OwnerName as NVARCHAR(128)
select ‘Name’ = name,
‘Owner’ = user_name(uid)
from sysobjects
where user_name(uid)=@OldOwner
order by name
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
END
deallocate curObject
GO
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:
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