當主查詢沒有返回記錄時，如何從子查詢獲取Count

Question

下面的MYSQL查詢為我提供了在主查詢中找到記錄時所需的輸出，例如

返回：

username  |  total_favs
this_user |  4

但如果在主查詢中找不到記錄，我什么都得不到。 我想得到這樣的東西：

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

切換它，所以favourites是主要查詢：

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