sql查询:如何用带标签的表过滤父标签和子标签？

Question

在从这个post获得正确答案后，我有一个进一步的问题-我必须进一步过滤行，即我必须确保标签必须标记到页面上。

这是我的root_mm_tagged_pages table

tag id  pg_id 
3       11  
5       11  
6       11  
18      12  
24      13  
26      13
3       14

所以我想返回这个结果，

ParentID    ParentName  TotalChildren   TotalTagged
3           Tagname-1   2               2
5           tagname-2   2               1
6           tagname-3   1               1
18          tagname-10  0               1
24          tagname-13  0               1
26          tagname-14  0               1

我尝试使用此查询，但得到一个错误- #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'COUNT( tagged.pg_id ) AS TotalTagged FROM root_tags AS parents LEFT OUTER JOI' at line 5，

SELECT 
    parents.tag_id AS ParentID,
    parents.tag_name AS ParentName,
    COUNT(childs.tag_id) AS TotalChildren
    COUNT( tagged.pg_id ) AS TotalTagged

FROM root_tags AS parents
    LEFT OUTER JOIN root_tags AS childs
    ON parents.tag_id = childs.parent_id

    LEFT OUTER JOIN root_mm_tagged_pages AS tagged
    ON tagged.tag_id = parents.tag_id

WHERE parents.parent_id IS NULL
GROUP BY parents.tag_id, parents.tag_name
ORDER BY parents.tag_id

我如何修复它并进一步过滤结果？

Answer 1

TotalChildren别名后缺少逗号。

SELECT 
    parents.tag_id AS ParentID,
    parents.tag_name AS ParentName,
    COUNT(childs.tag_id) AS TotalChildren , --You missed the comma here
    COUNT( tagged.pg_id ) AS TotalTagged
FROM root_tags AS parents
    LEFT OUTER JOIN root_tags AS childs
    ON parents.tag_id = childs.parent_id

    LEFT OUTER JOIN root_mm_tagged_pages AS tagged
    ON tagged.tag_id = parents.tag_id

WHERE parents.parent_id IS NULL
GROUP BY parents.tag_id, parents.tag_name
ORDER BY parents.tag_id