话不多说直接上代码：
代码语言：javascript复制 SELECT *
FROM `personrequireupdate` a LEFT JOIN (select p.*,o.officeid,o.name as officename from person_modifyinf p
LEFT JOIN office o on o.officeid=p.officeid)p ON p.personId=a.personId
LEFT JOIN personrole p2 ON a.personId = p2.personid
WHERE a.state=0 and p.state=0
这样它就会报错 ：
代码语言：javascript复制
SELECT *
FROM `personrequireupdate` a LEFT JOIN (select p.*,o.officeid ,o.name as officename from person_modifyinf p
LEFT JOIN office o on o.officeid=p.officeid)p ON p.personId=a.personId
LEFT JOIN personrole p2 ON a.personId = p2.personid
WHERE a.state=0 and p.state=0
> 1060 - Duplicate column name 'officeid'
> 时间: 0.083s改成这样子：
代码语言：javascript复制
SELECT *
FROM `personrequireupdate` a LEFT JOIN (select p.*,o.officeid AS offid,o.name as officename from person_modifyinf p
LEFT JOIN office o on o.officeid=p.officeid)p ON p.personId=a.personId
LEFT JOIN personrole p2 ON a.personId = p2.personid
WHERE a.state=0 and p.state=0
代码运行正常 ：
代码语言：javascript复制SELECT *
FROM `personrequireupdate` a LEFT JOIN (select p.*,o.officeid AS offid,o.name as officename from person_modifyinf p
LEFT JOIN office o on o.officeid=p.officeid)p ON p.personId=a.personId
LEFT JOIN personrole p2 ON a.personId = p2.personid
WHERE a.state=0 and p.state=0
> OK
> 时间: 0.059s看出为什么了吗？没错，就是因为在我们写关联语句时同样的字段出现了两次，没有给他们起别名引起的，就像我写的这个：o.officeid AS offid 。因此，在进行关联查询时，如果两张或几张表都有那同样的字段，要给它起个别名。
