sql - 具有 2 个联合的公用表表达式计数器

Question

如果我有一个包含母亲和父亲的家庭的公共(public)表表达式，我如何增加“世代”计数器？一个家庭应该将 child 作为第 0 代，将 parent 作为第 1 代，将四个祖 parent 作为第 2 代。但是循环执行两次，每组祖 parent 一次。

;WITH FamilyTree
AS
(
    SELECT *, 0 AS Generation
    FROM myTable
    WHERE [id] = 99

    UNION ALL
    SELECT name, Generation + 1
    FROM myTable AS Fam
    INNER JOIN FamilyTree
    ON Fam.[id] = FamilyTree.[motherid]

    UNION ALL
    SELECT name, Generation + 1
    FROM myTable AS Fam
    INNER JOIN FamilyTree
    ON Fam.[id] = FamilyTree.[fatherid]
)
SELECT generation, name FROM FamilyTree 

Answer 1

一次性更改对一代间隙中亲属的连接查看，而不是在 CTE 中使用 2 个递归子句。这两个子句形成部分交叉连接，这就是为什么你有额外的行

;WITH FamilyTree
AS
(
    SELECT *, 0 AS Generation
    FROM myTable
    WHERE [id] = 99

    UNION ALL
    SELECT name, Generation + 1
    FROM myTable AS Fam
    INNER JOIN FamilyTree
    ON Fam.[id] IN (FamilyTree.[motherid], FamilyTree.[fatherid])
)
SELECT generation, name FROM FamilyTree