MYSQL经典语句大全——技巧篇

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:
  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

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郑重声明:本文版权归原作者所有,转载文章仅为传播更多信息之目的,如作者信息标记有误,请第一时间联系我们修改或删除,多谢。

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