MySQL JOIN将PHP变量传递给两个表

Question

我在PHP中有以下MySQL查询，该查询传递变量以完成查询：

SELECT * from mobile_tech WHERE uid=$uid  order by timestamp DESC limit 0,1

我有以下MySQL JOIN，它提供来自两个表的数据：

SELECT mobile_tech.latitude, mobile_tech.longitude, mobile_tech.timestamp, mobile_tech.uid, gbl_qemplisting.EmpNo, gbl_qemplisting.FirstName, gbl_qemplisting.LastName 
FROM mobile_tech, gbl_qemplisting
WHERE mobile_tech.uid=gbl_qemplisting.EmpNo AND date(timestamp)='$currentday' 
group by uid

我需要将这两个查询与一个JOIN合并为一个，并仍然传递$ uid变量来完成查询。

我已经尝试了以下方法，但没有效果：

SELECT mobile_tech.latitude, mobile_tech.longitude, mobile_tech.timestamp, mobile_tech.uid, gbl_qemplisting.EmpNo, gbl_qemplisting.FirstName, gbl_qemplisting.LastName 
FROM mobile_tech, gbl_qemplisting
WHERE mobile_tech.uid=$uid AND gbl_qemplisting.EmpNo=$uid AND date(timestamp)='$currentday'

Answer 1

您的查询将返回之间的交叉产品mobile_tech和gbl_emplisting行为$uid 。 如果只需要一行，如在第一个查询中一样，则类似地使用ORDER BY和LIMIT 。

SELECT mobile_tech.latitude, mobile_tech.longitude, mobile_tech.timestamp, mobile_tech.uid, gbl_qemplisting.EmpNo, gbl_qemplisting.FirstName, gbl_qemplisting.LastName 
FROM mobile_tech, gbl_qemplisting
WHERE mobile_tech.uid=$uid AND gbl_qemplisting.EmpNo=$uid AND date(timestamp)='$currentday'
ORDER BY mobile_tech.timestamp
LIMIT 1

Answer 2

请尝试这个并说出结果

SELECT mobile_tech.latitude, 
mobile_tech.longitude, 
mobile_tech.timestamp,
mobile_tech.uid,
gbl_qemplisting.EmpNo,
gbl_qemplisting.FirstName,
gbl_qemplisting.LastName
FROM mobile_tech inner join gbl_qemplisting
        on mobile_tech.uid=gbl_qemplisting.EmpNo 
where mobile_tech.uid=$uid AND date(timestamp)='$currentday'