Question

我在Mysql 5.5版上。我有两张桌子 - 产品，ordr。

CREATE TABLE `product` (
  `id` int(11) NOT NULL,
  `name` varchar(45) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `ordr` (
  `id` int(11) NOT NULL,
  `product_id` varchar(45) DEFAULT NULL,
  `status` varchar(45) DEFAULT NULL,
  `qty` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

以下是它们的填充方式 -

insert into product values (20, 'pen');

insert into ordr values (100, 20, 'queue', 5);
insert into ordr values (110, 20, 'queue', 5);
insert into ordr values (120, 20, 'pending', 10);
insert into ordr values (130, 20, 'pending', 10);
insert into ordr values (140, 20, 'pending', 10);

我想获得两种不同状态的产品总数。对于上面数据的测试数据，我想看到10个队列数量，30个待处理数量。

当我跑步时

select p.name, sum(o.qty) as queue_qty, sum(o2.qty) as pending_qty
from product p
left outer join ordr o on o.product_id = p.id and o.status = 'queue'
left outer join ordr o2 on o2.product_id = p.id and o2.status = 'pending'
where p.id = 20;

我得到了

name - pen
queue_qty - 30
pending_qty - 60

有人可以帮我修复这个SQL吗？

Answer 1

您需要在信息加入之前汇总。由于您有两个1-n关系，因此您的连接逻辑会复制信息。

select
  p.name
  , o.qty as qty_queue
  , o2.qty as qty_pending
from
  product p
  join (
    select
      product_id
      , sum(qty) as qty
    from
      ordr
    where
      ordr.status = 'queue'
    group by
      product_id
  ) o
    on p.id = o.product_id
  join (
    select
      product_id
      , sum(qty) as qty
    from
      ordr
    where
      ordr.status = 'pending'
    group by
      product_id
  ) o2
    on p.id = o2.product_id
group by
  p.name

MySql - 从一个表中获取两组记录的总数

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