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2012年计算机三级数据库技术SQL语句辅导:技巧篇(2)

 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'

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