mysql - MySQL：同一个查询中的 SELECT 和 COUNT

Question

我有这两张表：

城市表

俱乐部桌

我要做的是使用相同的查询选择包含已发布俱乐部（published字段设置为 1）的所有城市以及该城市发布的俱乐部总数。

目前，我分两步进行，但我想通过将它们合并到一个查询中来提高性能。

SELECT c.id, c.name, c.slug 
FROM city c, club cl 
WHERE c.id = cl.city_id 
AND ( SELECT COUNT(*) 
      FROM club cl, city c 
      WHERE cl.city_id = c.id AND cl.published = 1) > 0
GROUP BY c.id

在此之后，我正在对每个城市进行查询以获取 COUNT。

Answer 1

像这样的东西： -

SELECT city.id, city.name, city.slug, COUNT(club.id) AS club_count
FROM city
INNER JOIN club
ON city.id = club.city_id
WHERE club.published = 1
GROUP BY city.id, city.name, city.slug
HAVING club_count > 0