当主查询没有返回记录时，如何从子查询获取Count

Question

下面的MYSQL查询为我提供了在主查询中找到记录时所需的输出，例如

返回：

username  |  total_favs
this_user |  4

但如果在主查询中找不到记录，我什么都得不到。 我想得到这样的东西：

返回：

username  |  total_favs
null |  4

SELECT 
  c.username,
  (SELECT COUNT(*) AS total_records FROM favourites f WHERE f.pic_id = 177) AS `total_favs`
FROM
  comments c
WHERE
  c.pic_id = 177

Answer 1

切换它，所以favourites是主要查询：

SELECT c.username, COUNT(*) AS total_favs
FROM favourites f
LEFT OUTER JOIN comments c on f.pic_id = c.pic_id
WHERE f.pic_id = 177
GROUP BY c.username