如何使用交叉連接比較連接表中的值？ MySQL的

Question

我想運行此查詢：

SELECT business.name as businessName i.ratingCount , i.ratingSum 
FROM business 
cross join 
    (
    SELECT SUM(rating.rating) as ratingSum,COUNT(rating.bussId) as ratingCount 
    FROM rating 
    WHERE rating.bussId = business.bussId 
)i 

，但我得到這個錯誤Unknown column 'business.bussId'！如何解決它？

I don't want to use left join ! 

Answer 1

你需要使用它作爲相關子查詢

SELECT business.name as businessName, 
     (select sum(rating.bussId) 
     from rating 
     where rating.bussId = business.bussId 
     ) as ratingSum, 
     (select count(rating.bussId) 
     from rating 
     where rating.bussId = business.bussId 
     ) as ratingCount 
FROM business 

，或者您可以使用左連接和

SELECT business.name as businessName, 
     sum(rating.bussId) as ratingSum, 
     count(rating.bussId) as ratingCount 
FROM business 
left join rating 
on business.bussId = rating.bussId 
group by business.name