Question

我一直试图找出在我的查询中添加其他变量的位置，以便正确地提取它，但我遇到了一些问题。这是我目前的查询：

SELECT
tt.unit_id,
tt.latitude,
tt.longitude,
tt.gps_settings,
tt.timestamp
FROM AA55 tt
LEFT JOIN device_link AS dl ON dl.device_id = unit_id
INNER JOIN (SELECT unit_id, MAX(timestamp) AS MaxTimestamp FROM AA55 GROUP 
BY unit_id) AS groupedtt
ON tt.unit_id = groupedtt.unit_id
AND tt.timestamp = groupedtt. MaxTimestamp
WHERE dl.user_id = '$real_id';

基本上，我需要从名为nickname的表中添加一个名为device_info的列。我已经尝试在tt.unit_id之后添加值，但我一直收到错误

Unknown column 'unit_id' in 'on clause'

需要通过将device_info.device_id与AA55.unit_id进行比较来获取昵称。

有没有办法做到这一点？提前谢谢。

Answer 1

这应该有效：

SELECT
tt.unit_id,
d2.nickname,
tt.latitude,
tt.longitude,
tt.gps_settings,
tt.timestamp
FROM AA55 AS tt
LEFT JOIN device_link AS dl ON(tt.unit_id=dl.device_id)
LEFT JOIN device_info AS d2 ON(tt.unit_id=d2.device_id)
INNER JOIN (SELECT unit_id, MAX(timestamp) AS MaxTimestamp FROM AA55    
GROUP BY unit_id) AS groupedtt
ON(tt.unit_id = groupedtt.unit_id)
AND tt.timestamp = groupedtt. MaxTimestamp
WHERE dl.user_id = '$real_id';

我正在尝试在查询

1 个答案: