sql 查询：如何过滤带有标签的表的父子标签？答案

【问题标题】：sql query: how to filter parent and children tags with a tagged table?sql 查询：如何过滤带有标签的表的父子标签？
【发布时间】：2011-08-04 21:08:05
【问题描述】：

从post 得到正确答案后，我还有一个问题 - 我必须进一步过滤该行，即我必须确保必须将标签标记到页面。

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，但出现错误 - #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

如何修复它并进一步过滤结果？

【问题讨论】：

标签： php mysql sql parent-child tagging

【解决方案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

【讨论】：

@lauthiamkok：在你来这里的 1 年里，你已经发布了 212 个问题——通常是一天几个问题——其中大部分只是为你寻找像这样愚蠢的错别字。在求助于他人之前，我可以建议增加调试代码的时间吗？这东西很琐碎！ :)