Question

我有下表

table prices
col id
col price
col currency_id
col timestamp (unix)

我想按照ID分组货币，只显示基于时间戳的最新记录。

我有以下查询正确分组但没有获得最新记录，似乎总是得到表中的第一行而不是最后一行。

SELECT 
id,
price,
currency_id,
timestamp
FROM prices
GROUP BY currency_id
ORDER BY timestamp DESC

我确实变得懒惰并尝试获取最后6条记录，但订单并不总是相同，这意味着每次添加新货币（目前为6）时我都必须修改查询。

SELECT 
id,
price,
currency_id,
timestamp
FROM prices
ORDER BY timestamp DESC
LIMIT 6

我做了任何MySQL已经有几年了，感觉这是最简单的事情lol :(

Answer 1

这是一个测试http://sqlfiddle.com/#!9/2a4e63/3

的sqlfiddle

从这开始：

SELECT currency_id, 
       Max(timestamp) 
FROM   prices 
GROUP  BY currency_id

然后将其集成到主查询：

SELECT * 
FROM   prices 
WHERE  ( currency_id, timestamp ) IN (SELECT currency_id, 
                                             Max(timestamp) 
                                      FROM   prices 
                                      GROUP  BY currency_id)

MySQL组最近的价值

1 个答案: