我有以下的疑問 -左加入乘值
SELECT COUNT(capture_id) as count_captures
FROM captures
WHERE user_id = 9
...返回5
SELECT COUNT(id) as count_items
FROM items
WHERE creator_user_id = 9
...返回22
我嘗試下面的查詢 -
SELECT COUNT(capture_id) as count_captures,
COUNT(items.id) as count_items
FROM captures
LEFT JOIN items ON captures.user_id = items.creator_user_id
WHERE user_id = 9
...但它返回兩個co列均以110爲值。我想要一列5,另一列22。我究竟做錯了什麼?
我一直都知道我可以跟一個子查詢,但你的第二個例子完美地工作。 – scott