根据结果​​递归查询和更改目标表

Question

假设我有一个类似的查询：

SELECT type_person FROM tbl_event WHERE id_animal = 1;

这给了我一个人的类型和要加入的目标表（在这种情况下，它将返回'worker'）从其他表中获取事件的完整数据，现在进行连接我知道我必须做一个加入'工人桌'，如：

SELECT  a.*,b.*,z.*
FROM    tbl_event a
        left JOIN tbl_worker b
            ON a.type_person = b.type_person
        left JOIN tbl_animal z
            ON   z.id_animal = a.id_animal 
        WHERE z.id_animal = 1;

有没有办法通过以下方式更改左边JOIN tbl_worker b的部分：

SELECT  a.*,b.*,z.*
FROM    tbl_event a
        left JOIN (SELECT type_person FROM tbl_event WHERE id_animal = 1)
            ON a.type_person = b.type_person
        left JOIN tbl_animal z
            ON   z.id_animal = a.id_animal 
        WHERE z.id_animal = 1;

here is a fiddle

Answer 1

当然，你需要做一些事情：

SELECT  a.*,b.*,z.*
FROM    tbl_event a
        left JOIN (SELECT type_person FROM tbl_event WHERE id_animal = 1) as b
            ON a.type_person = b.type_person
        left JOIN tbl_animal z
            ON   z.id_animal = a.id_animal 
        WHERE z.id_animal = 1;

基本上你错过了别名（在这种情况下是b）

Here's an updated fiddle

Answer 2

当然可以。你的意思是那样的

 SELECT  a.*,b.*,z.*
 FROM    tbl_event a
    left JOIN (SELECT type_person FROM tbl_event WHERE id_animal = 1) b
        ON a.type_person = b.type_person
    left JOIN tbl_animal z
        ON   z.id_animal = a.id_animal 
  where z.id_animal = 1;

DEMO

在您的查询中，您忘了制作AS b