MYSQL查询获取日期差

Question

我有一个带有以下列和数据的表事务

id  transaction_date trans_type account_id agents_id transaction_date price miles
1   2012-02-08       Buy        1          1         2010-02-08       0.016 12000
2   2012-03-01       Sell       2          2         2012-03-10       0.256 -2000
3   2012-03-27       Buy        3          3         2012-03-27       0.256 10000
4   2012-03-28       Sell       4          4         2012-03-28       0.589 -11000
5   2012-03-29       Buy        5          5         2012-03-29       0.87  25000
6   2012-03-29       Sell       6          6         2012-02-29       0.879 -12000
7   2012-04-01       Sell       7          7         2012-04-01       0.058 -15000

  Account Table
  id    Program_id
  1     1
  2     1
  3     2

  Program table
  id      Abbreviation
  1       AA
  2       AC

  Agents table
  id      Name
  1       Bob
  2       Ben

我想获取首次销售日期和首次购买日期，以获得交易出售前的平均天数，以获得交易在库存中的天数，所以应该是

  (Sell date)2012-03-01 - (Buy date)2012-02-08

我正在尝试这个

SELECT 
    case when t.trans_type ='Sell' then transaction_date end as SellDate
   ,case when t.trans_type ='Buy' then transaction_date end as BuyDate
   ,DATEDIFF(case when t.trans_type ='Sell' then transaction_date end
            ,case when t.trans_type ='Buy' then transaction_date end) as Date
   ,transaction_date
FROM transactions t
order by transaction_date

但日期总是为 NULL

这是完整的查询

SELECT p.abbreviation,ag.name
  ,sum(-1.00 * t.miles * t.price - coalesce(t.fees,0) - coalesce(c.cost,0)) as profit
  ,sum(t.miles) 'Totakl Miles'
  ,avg(price / miles) 'Average'
  ,transaction_date
FROM transactions t
inner join accounts a on t.account_id = a.id
inner join programs p on a.program_id = p.id
inner join agents ag on t.agent_id = ag.id
LEFT JOIN (
           SELECT rp.sell_id, sum(rp.miles * t.price) as cost
           from report_profit rp
           inner join transactions t on rp.buy_id = t.id
           where t.miles > 50000
           group by rp.sell_id
           order by rp.sell_id
          ) c on t.id = c.sell_id
where t.transaction_date BETWEEN '2012-03-14' AND '2012-04-14'
Group by p.id , ag.id

编辑

我尝试了liquvicar答案，但由于我添加了分组，所以出现错误“子查询返回多个记录”

有人可以指导我吗？

提前致谢...

Answer 1

尝试这样的子查询

SELECT 
    DATEDIFF(
      (
      SELECT MIN(date)
      FROM Transaction
      WHERE trans_type='Sell'
      ) AS first_sell_date
   ,
      (
      SELECT MIN(date)
      FROM Transaction
      WHERE trans_type='Buy'
      ) AS first_buy_date
   )

编辑:遵循OP评论并使用完整查询更新问题。

你不能只将 DATEDIFF 包裹在 MIN 调用中吗？

DATEDIFF(
    MIN(case when t.trans_type ='Sell' then transaction_date end),
    MIN(case when t.trans_type ='Buy' then transaction_date end)
) as Date