如何在此sql查詢中獲取所有祖先，所選類別和直接子項

Question

我想獲取所有祖先，所選類別和直接子項，並計算每個類別及其所有子項中的所有項目。

這是我做過什麼：

DECLARE @CategoryId INT = 8 
;WITH Re AS 
(
SELECT CategoryId, Name, ParentId, CategoryId RootId, 0 Depth, Sort = CAST(Name AS VARCHAR(MAX)) 
    FROM Category 
WHERE CategoryId = @CategoryId OR ParentId = @CategoryId 
UNION ALL 
SELECT C.CategoryId, C.Name, C.ParentId, RootId, Depth = Re.Depth + 1, Sort = Re.Sort + CAST(C.Name AS VARCHAR(200)) 
    FROM Re JOIN Category C ON Re.CategoryId = C.ParentId 
) 
SELECT Y.CategoryId, Y.Name, Y.ParentId, X.CatCount 
    FROM (SELECT RootId, COUNT(I.CategoryId) catCount 
      FROM Re LEFT OUTER JOIN Item I ON Re.CategoryId = I.CategoryId 
      GROUP BY RootId) X 
    JOIN (SELECT Re.CategoryId, Re.ParentId, Name, MAX(Depth) MaxDepth 
      FROM Re 
      GROUP BY Re.CategoryId, Re.ParentId, Name) Y ON Y.CategoryId = X.RootId 
ORDER BY CategoryId 

返回我想要什麼，但有一點問題是它。例如當@CategoryID = 8，此查詢應顯示：

CategoryId Name ParentId CatCount 
    0  A  NULL   16 
    1  B   0   10 
    7  H   1   4 
    8  I   7   2 
    13  N   8   1 

但它返回：當選擇子類別

CategoryId Name ParentId CatCount 
    8  I   7   2 
    13  N   8   1 

祖先未示出。

1. 問題在哪裏？
2. 如何優化此查詢？

我會感謝另外一個人幫助我

Answer 1

您的查詢不象你所說的，因爲與RootId問題（見下文評論） 你的CTE需要改變這個工作的：

DECLARE @CategoryId INT = 8 
;WITH Re AS 
(
    -- Anchor (this is the starting category) 
    SELECT CategoryId, Name, ParentId, CategoryId AS RootId, 
     0 AS Depth, Sort = CAST(Name AS VARCHAR(MAX)), CONVERT(VARCHAR(20), 'Root') AS Relation 
    FROM Category 
    WHERE CategoryId = @CategoryId 
    UNION ALL 
    -- Find children 
    SELECT C.CategoryId, C.Name, C.ParentId, C.CategoryId AS RootId, -- Fixed RootId problem 
     Depth = Re.Depth + 1, Sort = Re.Sort + CAST(C.Name AS VARCHAR(200)), CONVERT(VARCHAR(20), 'Child') AS Relation 
    FROM Re 
     INNER JOIN Category C ON Re.CategoryId = C.ParentId 
    WHERE Re.Relation IN('Root', 'Child') 
     -- I do not think this is necessary as we have established the anchor, see above 
     AND C.ParentId = @CategoryId 
    UNION ALL 
    -- Find Ancestors (Parents) 
    SELECT C.CategoryId, C.Name, C.ParentId, C.CategoryId AS RootId, -- Fixed RootId problem 
     Depth = Re.Depth - 1, Sort = Re.Sort + CAST(C.Name AS VARCHAR(200)), CONVERT(VARCHAR(20), 'Parent') AS Relation 
    FROM Re 
     INNER JOIN Category C ON C.CategoryId = Re.ParentId 
    WHERE Re.Relation IN('Root', 'Parent') 
) 
SELECT * FROM Re 

我已經使用了以下數據：

CREATE TABLE Category(CategoryId INT, Name VARCHAR(10), ParentID INT) 
SELECT * FROM Category 
INSERT INTO Category 
SELECT 0, 'A', NULL UNION ALL 
SELECT 1 , 'B', 0 UNION ALL 
SELECT 7 , 'H' , 1 UNION ALL 
SELECT 8 , 'I' , 7 UNION ALL 
SELECT 13 , 'N' , 8 
-- DROP TABLE Category