Question

一直在寻找构建一个mySQL查询，从多个不同的表中选择某些东西。但是，我在运行SQL时遇到错误。不确定我缺少什么

SQL：

SELECT * 
FROM tripreport as tr
JOIN 
(
   SELECT * FROM tripreportentries as tre LIMIT 1 
) ON tr.tripreportid = tre.reportid 
JOIN users as u ON tr.userid = u.id
JOIN user_details as ud ON u.id = ud.userid

错误：

Every derived table must have its own alias

我错过了一些非常明显的东西，这意味着每个表引用必须有自己的Alias，如我的查询中所定义的那样。对我来说，看起来所有的表都有这个，但它仍然无法运行？

我是误解了这个还是看不到什么？

Answer 1

你错过了别名：

....
JOIN 
(
   SELECT * FROM tripreportentries LIMIT 1 
) AS tre ON
...

Answer 2

使用()之外的别名。由于内部查询中只有一个表，因此您可以使用别名tre本身：

SELECT * 
FROM tripreport as tr
JOIN 
(
   SELECT * FROM tripreportentries LIMIT 1 
) as tre ON tr.tripreportid = tre.reportid 
JOIN users as u ON tr.userid = u.id
JOIN user_details as ud ON u.id = ud.userid

mySQL Multiple Joins

2 个答案: