Question

我有表products（id，name，price，...）和productStats（productId，{{1 }}，time，unitsSold，...）。

在unitsReserved中，我们每分钟都有一行，以及该特定分钟的所有必要汇总值。如果我们需要获得一个时期的统计数据，那就可以了：

productStats

但是当我们想要同时获取多个时段的聚合值时，我们遇到了错误（错误的值）：

select 
    id,
    name,
    SUM(lastDay.unitsSold) as latDayUnitsSold,
from `products`

left join 
    `productStats` as `lastDay` 
    on `products`.`id` = `lastDay`.`productId` 
    and `lastDay`.`time` between '2018-05-27 00:00:00' and '2018-05-28 00:00:00'

group by `products`.`id`

我们如何多次加入同一个表，但具有不同的日期时间范围，并且每个表都有单独的总和列？

Answer 1

尝试使用OR

在同一个连接表中添加所有不同的条件

select 
    id,
    name,
    SUM(lastDay.unitsSold) as latDayUnitsSold,
    SUM(lastMonth.unitsSold) as latMonthUnitsSold,
    SUM(lastYear.unitsSold) as latYearUnitsSold,
from `products`

left join 
    `productStats` as `lastDay` 
    on `products`.`id` = `lastDay`.`productId` 
    and 
    (
     `lastDay`.`time` between '2018-05-27 00:00:00' and '2018-05-28 00:00:00'
      OR
     `lastDay`.`time` between '2018-04-28 00:00:00' and '2018-05-28 00:00:00'
      OR 
      `lastDay`.`time` between '2017-05-28 00:00:00' and '2018-05-28 00:00:00'
    )
group by `products`.`id`

Answer 2

您可以使用单个连接操作

在不同的时间范围内使用条件聚合

SELECT 
    p.id,
    p.name,
    SUM(CASE WHEN `lastDay`.`time` BETWEEN '2018-05-27 00:00:00' AND '2018-05-28 00:00:00' THEN lastDay.unitsSold ELSE 0 END) AS latDayUnitsSold,
    SUM(CASE WHEN `lastDay`.`time` BETWEEN '2018-04-28 00:00:00' AND '2018-05-28 00:00:00' THEN lastDay.unitsSold ELSE 0 END) AS latMonthUnitsSold,
    SUM(lastDay.unitsSold) AS latYearUnitsSold,
FROM  `products` p
LEFT JOIN
    `productStats` AS `lastDay` 
    ON p.`id` = `lastDay`.`productId` 
    AND `lastDay`.`time` BETWEEN '2017-05-28 00:00:00' AND '2018-05-28 00:00:00'
GROUP BY p.id, p.name

mysql使用group by多次连接同一个表

2 个答案: