mysql - MySQL计数多个外键

所以我有一个查询，从'sites'表中选择，并使用外键计算'pages'的数量

SELECT s_id, s_name, s_main_url, COUNT(p_id) AS numpages
FROM sites
INNER JOIN pages ON sites.s_id = pages.site_id
GROUP BY pages.site_id
ORDER BY s_id ASC

我想添加另一个外键来计数，可能不止一个，所以我尝试了下面的

SELECT s_id, s_name, s_main_url, COUNT(p_id) AS numpages, COUNT(l_id) AS numlinks
FROM sites
INNER JOIN pages ON sites.s_id = pages.site_id
INNER JOIN links ON sites.s_id = links.site_id
GROUP BY pages.site_id, links.site_id
ORDER BY s_id ASC

numpages和numlinks的计数是相同的，它们似乎将所有表的结果相乘，并给了我一些不正确的大数字
有什么想法吗？

最佳答案

您应该考虑使用子选择，而不是连接和分组方式。

SELECT s_id, s_name, s_main_url, numpages, numlinks
FROM sites,
(SELECT COUNT(p_id) as numpages FROM pages WHERE pages.site_id = sites.s_id) as cnt_pages,
(SELECT COUNT(l_id) as numlink FROM links WHERE links.site_id = sites.s_id) as cnt_links
ORDER BY s_id ASC

关于mysql - MySQL计数多个外键，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/4659603/