MYSQL选择销售列出所有名称，即使它们没有出售[关闭]

Question

我需要选择商品的销售和金额。

我会使用脚本

select it.name
     , sum(sa.cash) 
  from items it 
  join sale sa 
    on it.id = sa.iditems
 where sa.time = '2020-11-10' 
 order 
    by it.nazev

这将列出我，例如

name   cash
Book   300
Mug    400

但是那天我有更多的商品不出售，我还需要列出它们，以便将 0 或 null 写为总和

结果应该是

Name   cash
Book   300
Mug    400
Soap    0
Cover   0
Sheet   0

谢谢

Answer 1

这是一个left join 和聚合：

select it.name, coalesce(sum(sa.cash) , 0) as cash
from items it 
left join sale sa on it.id = sa.iditems and sa.time = '2020-11-10' 
group by it.name
order by it.name

您也可以使用子查询来做到这一点：

select it.name,
    (select coalesce(sum(sa.cash) , 0) from sale sa where sa.iditems = it.id and sa.time = '2020-11-10') as cash
from items it
order by it.name