MySQL的：計數的孩子，讓父行

Question

我想算屬於一組父頁面和獲得父母的行，比如總項目，

pg_id  pg_title  parent_id 
1   A    1    
2   B    2 
3   C    3 
4   d    1 
5   e    1 
6   f    2 
7   g    1 
8   k    3 
9   l    3 
10  j    3 

所以我想這樣的結果，

ParentName ParentID  TotalCout 
A    1    3 
B    2    1 
C    3    3 

這裏是我到目前爲止出來的查詢，但它不返回的結果是正確的，這行的也沒有得到父母的網頁標題，但回到自己的孩子網頁標題相反，

SELECT root_pages.pg_title as ParentName,x.ParentID,x.TotalCount 
FROM 
(
SELECT root_pages.parent_id as ParentID, COUNT(root_pages.parent_id) as TotalCount 
FROM root_pages 
WHERE root_pages.parent_id != root_pages.pg_id 
AND root_pages.pg_hide != '1' 
GROUP BY root_pages.parent_id 
)x 

LEFT JOIN root_pages 
ON x.ParentID = root_pages.parent_id 

GROUP BY x.ParentID 

任何想法如何才能獲得我需要的正確結果？

謝謝

Answer 1

試試這個：

SELECT a.pg_title as ParentName, 
      a.pg_id as ParentID, 
      b.TotalCout 
    FROM root_pages a INNER JOIN 
     (
     SELECT parent_id, COUNT(1) as TotalCout 
      FROM root_pages 
      WHERE parent_id <> pg_id 
     GROUP BY parent_id 
     ) b 
    ON a.pg_id = b.parent_id 
    AND b.TotalCout>0 

Answer 2

我想你只是加入了錯誤的領域。試着加入x.parentid = root_pages.pg_id

Answer 3

select p.pg_title ParentName, p.pg_id ParentID, IFNULL(c.TotalCout,0) TotalCout 
from root_pages p 
left join 
(
    select parent_id, count(*) TotalCout 
    from root_pages 
    where parent_id != pg_id 
    group by parent_id 
) c on c.parent_id=p.pg_id 
WHERE p.pg_id = p.parent_id 

更改LEFT JOIN到INNER JOIN，如果你不感興趣的根（父）頁無子女。

在一個單一的選擇，給您的數據屬性，root := (parent_id=pg_id)

select max(case when pg_id=parent_id then pg_title end) ParentName, 
     parent_id ParentID, 
     count(*)-1 TotalCout 
from root_pages 
group by parent_id 
having count(*) > 1