如何避免在这里使用 while 循环？答案

【问题标题】：How do I avoid using a while loop here?如何避免在这里使用 while 循环？
【发布时间】：2012-08-20 08:14:14
【问题描述】：

作为一个从未从任何人那里得到过 SQL 指导/指导的人，我想听听你们应该如何进行以下查询。据我所知，像这样的循环是一种非常糟糕的做事方式。

我正在我的查询中创建一个表：

DECLARE @maxReleases int
SET @maxReleases = 100000

DECLARE @RootReleases table (ReleaseId int, RootReleaseId int)

DECLARE @ctr int
Set @ctr = 1

WHILE(@ctr <= @maxReleases)
BEGIN
WITH cte_Releases
( 
  ReleaseId,
  Name, 
  ParentReleaseID

) 
AS( 
  SELECT  
   ReleaseId, 
   Name,
   ParentReleaseID

  FROM Releases
  Where ReleaseId = @ctr

 UNION ALL 

 SELECT  
  R.ReleaseId,
  R.Name,
  R.ParentReleaseID 
 FROM Releases R
 INNER JOIN cte_Releases ON cte_Releases.ParentReleaseID = R.ReleaseId
) 
INSERT INTO @RootReleases 
SELECT max(ReleaseId) as ReleaseId, min(ReleaseId) as RootReleaseId FROM cte_Releases

SET @ctr = @ctr + 1
END

此代码的目的是构建一个表，将记录与其最远的父记录连接起来，并将其插入到一个表中，以便在查询的其他地方引用。

【问题讨论】：

标签： sql loops stored-procedures while-loop

【解决方案1】：

我没有要测试的数据，所以请告诉我，如果您按照这些思路运行会发生什么。应该可以使用 group by 和聚合。如果您提供示例数据，我可能会提供更多帮助。

     DECLARE @RootReleases table (ReleaseId int, RootReleaseId int)

;  WITH cte_Releases
( 
  ReleaseId,
  Name, 
  ParentReleaseID

) 
AS( 
  SELECT  
   ReleaseId, 
   Name,
   ParentReleaseID

  FROM Releases
 -- Where ReleaseId = @ctr

 UNION ALL 

 SELECT  
  R.ReleaseId,
  R.Name,
  R.ParentReleaseID 
 FROM Releases R
 INNER JOIN cte_Releases ON cte_Releases.ParentReleaseID = R.ReleaseId
) 
INSERT INTO @RootReleases 
SELECT max(ReleaseId) as ReleaseId, min(ReleaseId) as RootReleaseId FROM cte_Releases
WHERE ReleaseId BETWEEN 1 AND 100000
GROUP BY ReleaseId

【讨论】：