mysql - 来自同一个引用表的多个 sql 连接

Question

我目前有以下查询:

select  title,location,categorie,division, 
    reference.description as CA 
from emploi 
left join reference on emploi.categorie = reference.code_ref 
where id_type = 'CA' and emploi.status ='1'

我有第二个查询，它是相同的，但从引用表中获取不同的值:

select  title,location,categorie,division, 
    reference.description as DI 
from emploi 
left join reference on emploi.division = reference.code_ref 
where id_type = 'DI' and emploi.status ='1'

有没有办法执行这两个查询？

我认为这是类似于以下内容的内容，但它显然不起作用:

select  title,location,categorie,division, 
    reference.description as DI, reference.description as CA 
from emploi 
(left join reference on emploi.division = reference.code_ref 
    where id_type = 'DI')
(left join reference on emploi.categorie = reference.code_ref 
    where id_type = 'CA')
where emploi.status ='1'

谢谢!

注意:emploi 表中的每个条目都有一个部门和类别列，它们都需要映射到同一行上的单独条目

编辑:
对于那些感兴趣的人来说，这是可行的解决方案:

select  title,location,categorie,division, 
    r.description as DI, r1.description as CA 
from emploi 
left join reference r on emploi.division = r.code_ref 
    and r.id_type = 'DI'
left join reference r1 on emploi.categorie = r1.code_ref 
    and r1.id_type = 'CA'
where emploi.status ='1'

Answer 1

你可以试试这个:

select  title,location,categorie,division, 
    r.description as DI, r1.description as CA 
from emploi 
left join reference r on emploi.division = r.code_ref 
left join reference r1 on emploi.categorie = r1.code_ref 
where emploi.status ='1'
and id_type in ('CA', 'DI')

目前，您的语法不正确，因为您在 左连接 中使用了两次 where 子句。还将别名放入表中并使用这些别名来获取列名称

类似的东西

select  tablename.title,tablename.location,tablename.categorie,tablename.division, 
    r.description as DI, r1.description as CA 
from emploi 
left join reference r on emploi.division = r.code_ref 
left join reference r1 on emploi.categorie = r1.code_ref 
where emploi.status ='1'
and id_type in ('CA', 'DI')

注意:使用正确的表名称代替上面的tablename

编辑:-

如果您不想使用 IN 子句，那么

select  title,location,categorie,division, 
    r.description as DI, r1.description as CA 
from emploi 
left join reference r on emploi.division = r.code_ref 
    and r.id_type = 'DI'
left join reference r1 on emploi.categorie = r1.code_ref 
    and r1.id_type = 'CA'
where emploi.status ='1'

假设id_type是emploi的一列