不能加入两个以上的表

Question

我有3张桌子：

table1

fields : id, title, cat1_id

table2

fields : id, title, cat2_id

table3 

fields : id, title

我的SQL：

SELECT a.id, a.title, b.title, c.title 
FROM table1 AS a 
INNER JOIN table2 AS b ON b.id = a.cat1_id 
AND INNER JOIN table3 AS c ON c.id = b.cat2_id 
ORDER BY a.id DESC

它不起作用。

我尝试此SQL，它正在工作：

SELECT a.id, a.title, b.title, c.title 
FROM table1 AS a 
INNER JOIN table2 AS b ON b.id = a.cat1_id 
ORDER BY a.id DESC

但是双重INNER JOIN不起作用。

Answer 1

在JOIN之前，您不需要使用AND来连接两个以上的表。

您的查询应为

SELECT a.id, a.title, b.title, c.title 
FROM table1 AS a 
INNER JOIN table2 AS b ON b.id = a.cat1_id 
INNER JOIN table3 AS c ON c.id = b.cat2_id 
ORDER BY a.id DESC

看看MySQL JOIN语法