从联接表中选择每组的最新数据

Question

我有两张这样的表：

survey:
survey_id | store_code | timestamp

product_stock:
survey_id | product_code | production_month | value

如何根据调查时间戳并按 store_code、product_code 和 production_month 分组获得最新值？

例如，如果我有

survey_id | store_code | timestamp
1           store_1      2015-04-20
2           store_1      2015-04-22
3           store_2      2015-04-21
4           store_2      2015-04-22

survey_id | product_code | production_month | value
1           product_1      2                  15
2           product_1      2                  10
1           product_1      3                  20
1           product_2      2                  12
3           product_2      2                  23
4           product_2      2                  17

它会返回这样的结果

survey_id | store_code | time_stamp | product_code | production_month | value
2           store_1      2015-04-22   product_1      2                  10
1           store_1      2015-04-20   product_1      3                  20
1           store_1      2015-04-20   product_2      2                  12
4           store_2      2015-04-22   product_2      2                  17

而且它需要尽可能快，因为数据库的大小相当大

Answer 1

已更新 - 请再次运行查询

这是我的答案：

SELECT survey.survey_id, survey.store_code, survey.timestamp, product_stock.survey_id, product_stock.product_code, product_stock.production_month, product_stock.value 
FROM survey 
INNER JOIN product_stock
ON survey.survey_id = product_stock.survey_id
WHERE survey.timestamp = (SELECT MAX(timestamp) 
               FROM survey)
GROUP BY survey.store_code,product_stock.product_code,product_stock.production_month;