獲取其餘行

Question

請參閱下面的SQL查詢，它計算與numbers和business表匹配的總記錄數。

SELECT N.mobile, B.name, count(*) as Total FROM records as R 
LEFT JOIN business as B ON B.id = R.business_id 
LEFT JOIN numbers as N ON N.id = R.numbers_id 
group by N.mobile, B.name 

未包括在結果中。然而，也有剩餘的行（N.mobile, B.name），如何將它們與Total會是0？

Answer 1

你是說有沒有在​​records入口business和numbers行，但要包括他們在伯爵？由於MySQL不支持FULL OUTER JOIN使用UNION得到你想要的結果：

SELECT N.mobile, B.name, count(*) as Total FROM records as R 
LEFT JOIN business as B ON B.id = R.business_id 
LEFT JOIN numbers as N ON N.id = R.numbers_id 
GROUP BY N.mobile, B.name 

UNION 

SELECT N.mobile, NULL, 0 
FROM numbers AS N 
LEFT JOIN records as R ON N.id = R.numbers_id 
WHERE r.numbers_id IS NULL 

UNION 

SELECT NULL, B.Name, 0 
FROM business AS B 
LEFT JOIN records as R ON B.id = R.business_id 
WHERE r.business_id IS NULL 

Answer 2

用戶OUTER JOIN而不是INNER JOIN包括這些丟失的記錄：

SELECT N.mobile, B.name, count(*) as Total 
FROM records as R 
OUTER JOIN business as B ON B.id = R.business_id 
OUTER JOIN numbers as N ON N.id = R.numbers_id 
group by N.mobile, B.name