帶有2個聯合的公用表表達式計數器

Question

如果我有一個母親爲&父親的家庭的公用表表達式，我該如何增加'Generation'計數器？一個家庭應該讓孩子一代爲零，父母爲一代，父母代爲二代。但循環執行兩次，每組祖父母一次。

;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

一次性改變連接查看一代親代中的親戚，而不是在CTE中有2個遞歸子句。這兩個子句形成了一個部分交叉連接，這就是爲什麼你有多餘的行

;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