SQL Recursive CTE - 保持对父级的引用答案

【问题标题】：SQL Recursive CTE - Keep reference to a parentSQL Recursive CTE - 保持对父级的引用
【发布时间】：2015-01-10 02:38:31
【问题描述】：

我有一个结构如下的表

userId      userName         managerId
----------- ---------------- -----------
1           John             NULL
2           Charles          1
3           Nicolas          NULL
4           Neil             3

我还有另一个表，其中包含以下内容

userId      shareId         
----------- -----------
1           1001             
3           1002

所以我执行以下查询来获取我的递归 CTE：

WITH UserCTE AS (
  SELECT userId, userName, managerId,0 AS steps
  FROM dbo.Users
  WHERE userId = 7

  UNION ALL

  SELECT mgr.userId, mgr.userName, mgr.managerId, usr.steps +1 AS steps
  FROM UserCTE AS usr
    INNER JOIN dbo.Users AS mgr
      ON usr.managerId = mgr.userId
)
SELECT * FROM UserCTE AS u;

产生以下结果

userId      userName         managerId   steps       
----------- ---------------- ----------- ----------- 
1           John             NULL        0           
2           Charles          1           1           
3           Nicolas          NULL        0           
4           Neil             3           1

好的，我想知道shareId 对于拥有它的用户以及属于他们的用户。

预期结果：

userId      userName         managerId   steps       shareId
----------- ---------------- ----------- ----------- ----------
1           John             NULL        0           1001
2           Charles          1           1           1001
3           Nicolas          NULL        0           1002
4           Neil             3           1           1002

有什么方法可以实现吗？

谢谢

【问题讨论】：

标签： sql-server tsql sql-server-2012

【解决方案1】：

在Recursive CTE 的锚查询中加入Share table 与Users 表。试试这个。

;WITH UserCTE
     AS (SELECT c.userId,
                userName,
                managerId,
                0 AS steps,
                shareId
         FROM   dbo.Users c
                LEFT JOIN share_table s
                  ON c.userId = s.userId
         WHERE  managerId IS NULL
         UNION ALL
         SELECT mgr.userId,
                mgr.userName,
                mgr.managerId,
                usr.steps + 1 AS steps,
                usr.shareId
         FROM   UserCTE AS usr
                INNER JOIN dbo.Users AS mgr
                        ON usr.userId = mgr.managerId)
SELECT *
FROM   UserCTE AS u
ORDER  BY userId;

【讨论】：

非常感谢，这正是我想要的。

【解决方案2】：

你可以在 cte 表和 usershare 表上做left join。

WITH UserCTE AS (
  SELECT userId, userName, managerId,0 AS steps
  FROM dbo.Users
  where   managerId IS NULL

  UNION ALL

  SELECT mgr.userId, mgr.userName, mgr.managerId, usr.steps +1 AS steps
  FROM UserCTE AS usr
  INNER JOIN dbo.Users AS mgr
  ON usr.userId = mgr.managerId
  )
SELECT * FROM UserCTE AS u
left join userShare us
on u.managerId = us.userId
or u.userId = us.userId
order by u.userId

【讨论】：

【解决方案3】：

一种方法是在UserCTE 表和share 表之间的连接中使用OR。例如：

WITH UserCTE AS (
  SELECT userId, userName, managerId,0 AS steps
  FROM dbo.Users
  WHERE userId = 7

  UNION ALL

  SELECT mgr.userId, mgr.userName, mgr.managerId, usr.steps +1 AS steps
  FROM UserCTE AS usr
    INNER JOIN dbo.Users AS mgr
      ON usr.managerId = mgr.userId
)
SELECT * FROM UserCTE AS u
INNER JOIN [share table] AS s
    ON u.userId = s.userId OR u.managerId s.userId;

但是，如果存在多于一级的管理层次结构，这可能会处理重复。 IE。经理也有经理。另一种方法是在UserCTE 表的userId 列上进行两个左连接，一个到share 表，另一个到UserCTE 表的managerId 列到share 表。然后，您可以在shareId 列上使用CASE 语句来决定您需要哪一个。见下文：

WITH UserCTE AS (
  SELECT userId, userName, managerId,0 AS steps
  FROM dbo.Users
  WHERE userId = 7

  UNION ALL

  SELECT mgr.userId, mgr.userName, mgr.managerId, usr.steps +1 AS steps
  FROM UserCTE AS usr
    INNER JOIN dbo.Users AS mgr
      ON usr.managerId = mgr.userId
)
SELECT
    u.*
    ,CASE 
        WHEN su.shareId is not null THEN su.shareId
        WHEN sm.shareId is not null THEN sm.shareId
        ELSE null END as shareID
FROM UserCTE AS u
LEFT JOIN [share table] AS su
    ON u.userId = s.userId
LEFT JOIN [share table] AS sm
    ON u.managerId = s.userId;

希望这会有所帮助。

【讨论】：