无法加入两个以上的表

Question

我有3个表：

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 

它不工作。

我试试这个SQL，它的工作：

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 

但双INNER JOIN不起作用。

Answer 1

您不需要在JOIN之前使用AND来加入更多的两个表。

您的查询应该是

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 

看一看MySQL JOIN Syntax