SQL父子查询不起作用

Question

I want to get parent and their child data,means first come parent then their childs,Below is query that i want to convert to parent and their child

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'

I try below query

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

after executing these query i got this error

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'.

Then i change my query and remove count(*)

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 

then i got this error

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

Answer 1

Actually it is by design, read Guidelines for Defining and Using Recursive Common Table Expressions

The following items are not allowed in the CTE_query_definition of a recursive member:

• SELECT DISTINCT
• GROUP BY
• HAVING
• Scalar aggregation
• TOP
• LEFT, RIGHT, OUTER JOIN (INNER JOIN is allowed)
• Subqueries

You have to move your LEFT JOINs and COUNT out of the CTE query, store those data somewhere else (like in a temp table) and then later use those with the result of your CTE query. Or you can avoid CTE query and do this step by step separately for each level of parent-child, store in separate temp tables and use the results. Hope that helps.