Question

我有一个查询如下

SELECT 
sum(price), 
count(id), 
sum case(when spec='bath' then price else 0 END) as bath_money    
FROM 
table1
LEFT JOIN table2 ON table1.id = table2.fkt1
LEFT JOIN table3 ON table2.id = table3.fkt2    
WHERE 1    
group by sale;

现在我的问题是表3在表2中每行有2行。表2是我实际用于累加销售额和总和价格的那一行但由于我需要为表3保留连接，所以一切都添加了两次。是否有办法将表2的价格加起来而忽略了加入表3所产生的所有双线？否则我只是写另一个查询，但我想知道我是否可以做一个忽略特定连接的总和？

Answer 1

您可以尝试类似

的内容

SELECT 
sum(t1.price), 
count(t1.id), 
sum (case when t2.spec='bath' then t2.price else 0 END) as bath_money

FROM 
table1 t1
LEFT JOIN table2 t2 ON t1.id = t2.fkt1
LEFT JOIN table3 t3 ON t2.id = t3.fkt2

group by t1.sale

Answer 2

这是否有效：

SELECT 
sum(price), 
count(id), 
sum(case when spec='bath' then price else 0 END) as bath_money    
FROM table1 t1
LEFT JOIN table2 ON table1.id = table2.fkt1
LEFT JOIN (select * from table3 GROUP BY fkt2) table3a ON table2.id = table3a.fkt2    
group by sale;

具有不同组条件的JOINED表上的mysql和

2 个答案: