SQL查询将为

$sql = "SELECT t1.user_id FROM table1 AS t1 
                   JOIN table2 AS t2
                   ON t2.area_id = 3 
                   WHERE t1.cat_id = 11"

$this->query($sql);

有关文档，请参阅此处

你可以在表之间使用INNER JOIN，查询将是：

SELECT t1.*, t2.* FROM table1 t1 INNER JOIN table2 t2 ON t1.user_id = t2.user_id

CakePHP有自己的ORM，你可以在这里查看：
简单查询。
http://book.cakephp.org/3.0/en/orm/query-builder.html#selecting-rows-from-a-table
关联：
http://book.cakephp.org/3.0/en/orm/query-builder.html#loading-associations
祝你好运

SELECT user_id 
FROM table1, table2 
WHERE table1.cat_id = 2 and table2.area_id = 3

“我知道，我知道，我大伯已经告诉我了。”