我有一个交易所清单,有汇率和日期,每天都会更新,
示例->
usd - 135 - 26/02/2013
Yen - 230 - 26/02/2013
GBP - 200 - 26/02/2013
usd - 136 - 25/02/2013
Yen - 230 - 25/02/2013
GBP - 205 - 25/02/2013
我有一个查询将它们组合起来,查询是这样的->
SELECT Curr, Src, GROUP_CONCAT(Rate, '|', Feeddate
ORDER BY feeddate ASC SEPARATOR ',' ) AS RateCal
FROM rates
所以看起来像这样->
usd - 135 | 26/02/2013, 136 | 25/02/2013
Yen - 230 | 26/02/2013, 230 | 25/02/2013
GBP - 200 | 26/02/2013, 206 | 25/02/2013
但我也有一个查询来获取每个月每个交易所的平均值,这就是 ->
SELECT Curr, DATE_FORMAT(Feeddate,'%Y-%M') AS 'Year', AVG(`Rate`) as 'Rate'
FROM rates,
但我现在想要的是像上面一样拥有每个交换组 concat 的月平均值