mysql - 查找不同日期的价格差异

Question

如何找到两个选定日期的价格差异。我的桌子如图

---------------------------------------
id      price      date        product
---------------------------------------
1       10         15-12-2013  pen
2       40         15-12-2013  book
3       15         16-12-2013  pen
4       42         16-12-2013  book
-------------------------------------

我想要一个 sql 查询来获取输出，例如，如果 startdate:15-12-2013 & enddate:16-12-2013

product  startdate(15-12-2013)  enddate(16-12-2013) difference
--------------------------------------------------------------
pen        10                      15                  5
book       40                      42                  2
--------------------------------------------------------------

Answer 1

也许是这样的？

select
        p1.product,
        p1.price,
        p2.price,
        p1.price - p2.price as diff
from
        product p1,
        product p2
where
        p1.product=p2.product and
        date(p1.date)='2013-12-15' and
        date(p2.date)='2013-12-16'

如果性能是一个问题，那么此链接可以为日期匹配部分提供更好的替代方案：MySQL SELECT WHERE datetime matches day (and不一定是时间)

Answer 2

尝试这个：

SELECT product, StartDatePrice, EndDatePrice, (EndDatePrice - StartDatePrice) AS Difference 
FROM (SELECT product, MAX(IF(a.date = '15-12-2013', a.price, 0)) AS StartDatePrice, 
             MAX(IF(a.date = '16-12-2013', a.price, 0)) AS EndDatePrice 
      FROM tableA a 
      GROUP BY product
     ) AS A;

Answer 3

如果您在价格变化时（而不是每天）在价格表中插入一行，则应考虑使用此查询：

SELECT
  p1.product,
  p1.price as stardtade,
  p2.price as enddate,
  p2.price-p1.price as difference
FROM
  prices p1 INNER JOIN (SELECT product, MAX(dt) max_dt
                        FROM prices
                        WHERE dt<='2013-12-15'
                        GROUP BY product) st
  ON p1.product=st.product AND p1.dt = st.max_dt

  INNER JOIN

  prices p2 

  ON p1.product=p2.product

  INNER JOIN (SELECT product, MAX(dt) max_dt
                        FROM prices
                        WHERE dt<='2013-12-16'
                        GROUP BY product) ed
  ON p2.product=ed.product AND p2.dt = ed.max_dt

它更复杂，但即使您的表格中不存在某些日期，它也会起作用。在这种情况下，它将使用价格的 lask 已知值。

请在此处查看小提琴。