当主查询没有返回记录时，如何从子查询获取Count

Question

The MYSQL query below gives me the output I need when there are records found in the main query eg

RETURN:

username  |  total_favs
this_user |  4

But I get nothing return if no records found in main query. I want to get something like this:

RETURN:

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

Switch it around so favourites is the main query:

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