Sql Join和Sum

Question

我试图使用左连接从两个不同的表中总计一个数量.无论第二个表是否匹配,我都需要返回所有行.

   SELECT l.tender, 
          l.starting+SUM(t.amount) AS 'amount' 
     FROM label l 
LEFT JOIN transfers t on l.tender=t.name 
 ORDER BY l.tender

Answer 1

这应该工作:

SELECT  l.tender, 
        l.starting + ISNULL(t.amount,0) AS amount
FROM label l 
LEFT JOIN ( SELECT name, SUM(amount) amount
            FROM transfers
            GROUP BY name) t 
    ON l.tender = t.name 
ORDER BY l.tender