我有 3 张桌子;合同、经销商和用户。
用户有很多经销商,经销商有很多合同,但合同与用户没有直接关联。
我正在尝试构建一个报告,让我每月统计过去 12 个月内按用户分组的已完成合同。
到目前为止,我已经构建了一个非常慢的多个子查询:SQL Fiddle
SELECT *,
( SELECT count(*) FROM contracts
WHERE
dealer_id IN
( SELECT id FROM dealers WHERE user_id = User.id )
AND status = 'Paid'
AND completion_date BETWEEN
'2012-08-01 00:00:00' AND '2012-08-31 23:59:59'
) AS Aug_2012,
( SELECT count(*) FROM contracts
WHERE
dealer_id IN
( SELECT id FROM dealers WHERE user_id = User.id )
AND status = 'Paid'
AND completion_date BETWEEN
'2012-09-01 00:00:00' AND '2012-09-30 23:59:59'
) AS Sep_2012
FROM users AS User
WHERE
id IN( SELECT user_id FROM dealers WHERE active = 1 AND user_id IS NOT NULL GROUP BY user_id )
AND id != 1
ORDER BY User.name ASC
而不是选择每个月的子查询,我想使用这样的东西:
COUNT(*) as last_12_months,
SUM(case when MONTH(completion_date) = 8 then 1 else 0 end) as Aug_2012,
SUM(case when MONTH(completion_date) = 9 then 1 else 0 end) as Sep_2012,
etc.
由于我将返回多个列,因此我将不得不对其进行重组,但我不确定如何。如果我使用 INNER JOIN 加入什么子句?
以下是基于米哈伊尔回答的最终查询:
SELECT
User.*,
SUM(case when MONTH(completion_date) = 8 then 1 else 0 end) AS Aug_2012,
SUM(case when MONTH(completion_date) = 9 then 1 else 0 end) AS Sep_2012,
SUM(case when MONTH(completion_date) = 10 then 1 else 0 end) AS Oct_2012,
SUM(case when MONTH(completion_date) = 11 then 1 else 0 end) AS Nov_2012,
SUM(case when MONTH(completion_date) = 12 then 1 else 0 end) AS Dec_2012,
SUM(case when MONTH(completion_date) = 1 then 1 else 0 end) AS Jan_2013,
SUM(case when MONTH(completion_date) = 2 then 1 else 0 end) AS Feb_2013,
SUM(case when MONTH(completion_date) = 3 then 1 else 0 end) AS Mar_2013,
SUM(case when MONTH(completion_date) = 4 then 1 else 0 end) AS Apr_2013,
SUM(case when MONTH(completion_date) = 5 then 1 else 0 end) AS May_2013,
SUM(case when MONTH(completion_date) = 6 then 1 else 0 end) AS Jun_2013,
SUM(case when MONTH(completion_date) = 7 then 1 else 0 end) AS Jul_2013,
SUM(case when completion_date BETWEEN '2012-08-01 00:00:00' AND '2013-07-31 23:59:59' then 1 else 0 end) as last_12_months
FROM users AS User
LEFT OUTER JOIN
(
SELECT id, user_id FROM dealers
WHERE active = 1 AND user_id IS NOT NULL
) AS Dealer ON User.id = Dealer.user_id
LEFT OUTER JOIN
(
SELECT completion_date, status, dealer_id FROM contracts
WHERE completion_date BETWEEN '2012-08-01 00:00:00' AND '2013-07-31 23:59:59' AND status = 'Paid' AND cancelled = 0
) AS Contract on Dealer.id = Contract.dealer_id
WHERE
User.id IN
(
SELECT user_id FROM dealers
WHERE active = 1 AND user_id IS NOT NULL
GROUP BY user_id
)
GROUP BY
User.id order by User.name asc
这大约快 4 倍。