php – 1054完全加入的未知列,但不是其他联接

为什么我从以下mysql语法中得到“1054 UnkNown Column error”：

SELECT attorney_first_name, attorney_last_name, att_school, att_degree_obtained
FROM jos_legalally_attorneys
FULL JOIN jos_legalally_attorney_education
ON jos_legalally_attorneys.user_id=jos_legalally_attorney_education.user_id;

它导致错误：

#1054 - UnkNown column 'jos_legalally_attorneys.user_id' in 'on clause' 

尝试完全加入时,我只收到此错误.使用此精确语法时,所有其他连接(内部,右侧,左侧)都是成功的. (我尝试了FULL OUTER JOIN变体).

解决方法:

报告为here,MysqL不支持FULL JOIN,因此您的查询解释如下：

SELECT attorney_first_name, attorney_last_name, att_school, att_degree_obtained
FROM jos_legalally_attorneys as FULL #FULL is taken as table alias!!
INNER JOIN jos_legalally_attorney_education
ON jos_legalally_attorneys.user_id=jos_legalally_attorney_education.user_id;

现在,因为它具有FULL作为jos_legalally_attorneys的表别名,所以它无法正常工作.

如果您尝试以下查询,它应该没有错误(即使它没有做你想要的)：

SELECT attorney_first_name, attorney_last_name, att_school, att_degree_obtained
FROM jos_legalally_attorneys
FULL JOIN jos_legalally_attorney_education
ON FULL.user_id=jos_legalally_attorney_education.user_id;

现在,为了获得MysqL所需的FULL JOIN,你需要做这样的事情(如图所示)：

SELECT attorney_first_name, attorney_last_name, att_school, att_degree_obtained
FROM jos_legalally_attorneys
LEFT JOIN jos_legalally_attorney_education
ON jos_legalally_attorneys.user_id=jos_legalally_attorney_education.user_id
UNION ALL
SELECT attorney_first_name, attorney_last_name, att_school, att_degree_obtained
FROM jos_legalally_attorneys
RIGHT JOIN jos_legalally_attorney_education
ON jos_legalally_attorneys.user_id=jos_legalally_attorney_education.user_id