Sql父子查询不起作用

Posted 2023-02-24

【中文标题】Sql父子查询不起作用

【英文标题】：Sql parent Child Query not working

【发布时间】：2015-11-13 06:08:04

【问题描述】：

我想获取父母和他们的孩子数据，意味着先来父母然后他们的孩子，下面是我想转换为父母和他们的孩子的查询

SELECT a.FactorTitle,
       a.FactorCode,
       a.parentId,
       c.FactorColumnCode,
       c.FactorColumnTitle,
       c.FactorColumnValue,
       c.isFactorValue,
       c.FieldType,

  (SELECT count(*)
   FROM FactorSetup
   WHERE parentId=a.FactorCode) AS childCount
FROM FactorSetup a
INNER JOIN PDModelSetup b ON a.PDModelCode=b.PDModelCode
LEFT JOIN FactorColumnSetup c ON a.FactorCode=c.FactorCode
WHERE a.PDModelCode=2
  AND c.isFactorValue <> 'Y'
  AND a.FactorType='4'

我试试下面的查询

WITH EntityChildren AS
  (
   SELECT  a.FactorTitle,
           a.FactorCode,
           a.parentId,
           c.FactorColumnCode,
           c.FactorColumnTitle,
           c.FactorColumnValue,
           c.isFactorValue,
           c.FieldType,

  (SELECT count(*)
   FROM FactorSetup
   WHERE parentId=a.FactorCode) AS childCount
   FROM FactorSetup a
   LEFT JOIN FactorColumnSetup c ON a.FactorCode=c.FactorCode
   UNION ALL 
   SELECT a.FactorTitle,
           a.FactorCode,
           a.parentId,
           c.FactorColumnCode,
           c.FactorColumnTitle,
           c.FactorColumnValue,
           c.isFactorValue,
           c.FieldType,

  (SELECT count(*)
   FROM FactorSetup
   WHERE parentId=a.FactorCode) AS childCount
   FROM FactorSetup a

   INNER JOIN EntityChildren e2 ON a.parentId = e2.FactorCode
   LEFT JOIN FactorColumnSetup c ON a.FactorCode=c.FactorCode
   )

SELECT * FROM EntityChildren

执行这些查询后我得到了这个错误

Msg 467, Level 16, State 1, Line 1
GROUP BY, HAVING, or aggregate functions are not allowed in the recursive part of a recursive common table expression 'EntityChildren'.
Msg 462, Level 16, State 1, Line 1
Outer join is not allowed in the recursive part of a recursive common table expression 'EntityChildren'.

然后我更改我的查询并删除计数（*）

WITH EntityChildren AS
  (
   SELECT  a.FactorTitle,
           a.FactorCode,
           a.parentId,
           c.FactorColumnCode,
           c.FactorColumnTitle,
           c.FactorColumnValue,
           c.isFactorValue,
           c.FieldType
   FROM FactorSetup a
   LEFT JOIN FactorColumnSetup c ON a.FactorCode=c.FactorCode
   UNION ALL 
   SELECT a.FactorTitle,
           a.FactorCode,
           a.parentId,
           c.FactorColumnCode,
           c.FactorColumnTitle,
           c.FactorColumnValue,
           c.isFactorValue,
           c.FieldType
   FROM FactorSetup a

   INNER JOIN EntityChildren e2 ON a.parentId = e2.FactorCode
   LEFT JOIN FactorColumnSetup c ON a.FactorCode=c.FactorCode
   )

SELECT * FROM EntityChildren 

然后我得到了这个错误

Msg 462, Level 16, State 1, Line 1
Outer join is not allowed in the recursive part of a recursive common table expression 'EntityChildren'.

【参考方案1】：

其实是设计的，看Guidelines for Defining and Using Recursive Common Table Expressions

以下项目是不允许在一个 CTE_query_definition 递归成员：

选择不同的 分组依据 有 标量聚合 顶部 左、右、外连接（允许内连接） 子查询

您必须将 LEFT JOIN 和 COUNT 从 CTE 查询中移出，将这些数据存储在其他地方（例如临时表中），然后将这些数据与 CTE 查询的结果一起使用。或者您可以避免 CTE 查询，并为每个父子级别分别执行此操作，存储在单独的临时表中并使用结果。希望对您有所帮助。

【讨论】：

顺便说一句，在这里找到类似的东西：***.com/questions/9126704/… 您可以尝试将 LEFT JOIN 替换为 OUTER APPLY。