加入4桌在MySQL中，最大行从一个表

Question

我在MySQL数据库中的四个表，我试图创建一个连接所有四个从日志表拉动的最新数据查询：

• 评级（ID，等级，设备ID，listingId）
• 数据（listingId，名称，位置）
• 设备（设备ID，型号）
• 日志（dateAdded，DEVICEID，appVersion）

我想显示： 评级，名称，地点，型号，应用程序版本

应用程序版本随时间变化，因此它与设备表保持分离。

以下查询让我在那里的一半。问题是appVersion不是最新的。

SELECT ratings.id,ratings.listingId,ratings.rating,data.name,devices.model,tt.appVersion 
FROM ratings 
JOIN data on ratings.listingId = data.id 
JOIN devices on ratings.deviceIdentifier = devices.deviceIdentifier 
JOIN (select max(dateAdded), appVersion, deviceIdentifier from logs) tt 
ORDER BY dateAdded DESC; 

如果我尝试以下任一语句，查询将超时。

SELECT ratings.id,ratings.listingId,ratings.rating,data.name,devices.model,tt.appVersion 
FROM ratings 
JOIN data on ratings.listingId = data.id 
JOIN devices on ratings.deviceIdentifier = devices.deviceIdentifier 
JOIN (select max(dateAdded), appVersion, deviceIdentifier from logs where dateAdded in  
(select max(dateAdded) from logs group by deviceIdentifier)) tt 
ORDER BY dateAdded DESC; 

或

SELECT ratings.id,ratings.listingId,ratings.rating,data.name,devices.model,logs.appVersion 
FROM ratings 
JOIN data on ratings.listingId = data.id 
JOIN devices on ratings.deviceIdentifier = devices.deviceIdentifier 
JOIN (select t.deviceIdentifier, t.appVersion 
    from logs t 
    inner join (select deviceIdentifier, max(dateAdded) as dateAdded from logs 
      group by deviceIdentifier) x 
      on t.deviceIdentifier = x.deviceIdentifier and t.dateAdded = x.dateAdded) tt 
ORDER BY dateAdded DESC; 

Answer 1

编辑：修正小bug。我已经测试过这个，它工作。

set @deviceId := 0; 
select * 
from (select r.id, r.listingId, r.rating, data.name, d.model, d.deviceId, l.appVersion 
    FROM ratings r 
    JOIN data on r.listingId = data.listingId 
    JOIN devices d on r.deviceId = d.d eviceId 
    JOIN logs l on l.deviceId = d.deviceId 
    ORDER BY d.deviceId, dateAdded DESC) x 
where @deviceId != deviceId 
and (@deviceId := deviceId) is not null;