如何在TSQL中使用循环？

Question

在TSQL中,我想更改以下代码,必须使用硬编码的dhomes来使用循环进行优化.我还尝试添加循环失败.

Declare  @dhome Tinyint, @bp smallint, @lr smallint, @q smallint

    // Set @dhome = 1
  While(@dhome <= 3) // My attempt to add a loop

  SELECT @lr = MAX(NQdDate), @q = NQd
  FROM NQdHistory
  WHERE dhomeId = @dhome 
  GROUP BY NQdDate, NQd

  SELECT @bd = COUNT(*)
  FROM bdhome
  WHERE NQdDate= @lr AND dhomeID= @dhome 

  DELETE FROM ND1 WITH(XLOCK)
  WHERE dhomeID= @dhome  AND NQdDate= @lr

  UPDATE NQdHistory
  SET Nbd = @q - @@RowCount - @bp, NBd = @bp
  WHERE NQdDate= @lr AND dhomeID= @dhome 

  Set @dhome = @dhome +1 //My attempt to end a loop

Answer 1

你走在正确的轨道上.你错过了你的开始和结束.另外,一定要给出@dhome一个值.看起来你已经开始并在第三行评论了它:

Declare  @dhome Tinyint, @bp smallint, @lr smallint, @q smallint

    // Set @dhome = 1
While(@dhome <= 3) // My attempt to add a loop
begin
  SELECT @lr = MAX(NQdDate), @q = NQd
  FROM NQdHistory
  WHERE dhomeId = @dhome 
  GROUP BY NQdDate, NQd

  SELECT @bd = COUNT(*)
  FROM bdhome
  WHERE NQdDate= @lr AND dhomeID= @dhome 

  DELETE FROM ND1 WITH(XLOCK)
  WHERE dhomeID= @dhome  AND NQdDate= @lr

  UPDATE NQdHistory
  SET Nbd = @q - @@RowCount - @bp, NBd = @bp
  WHERE NQdDate= @lr AND dhomeID= @dhome 

  Set @dhome = @dhome +1 //My attempt to end a loop
end  

如果你熟悉C/C#/ C++,认为T-SQL的BEGIN和END像花括号{和},如果你更熟悉VB Then和End If.或者更像是帕斯卡Begin和End.你明白了:)