php – 1054完全加入的未知列,但不是其他联接

发布时间：2020-12-13 16:54:36 所属栏目：PHP教程来源：网络整理

导读：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_obtainedFROM jos_legalally_attorneysFULL JOIN jos_legalally_attorney_educationON jos_legalally_attorneys.user

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,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,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,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,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

（编辑：李大同）

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