1054在全未知列加入，而不是其他加盟

Question

为什么我得到了下面的MySQL语法“1054未知列错误”：

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' 

我只在尝试FULL JOIN时遇到此错误。使用这种精确的语法时，所有其他联接（Inner，Right，Left）都是成功的。 （我尝试了FULL OUTER JOIN变化）。

Answer 1

现报道here，MySQL不支持FULL JOIN，所以你的查询解释如下：

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，因为它有FULL为jos_legalally_attorneys表的别名，它不能正常工作。

如果您尝试以下查询，它应该给没有错误（尽管它不会做你想要的）：现在

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; 

，为了得到FULL JOIN需要MySQL，你下需要做这样的事情（如图所示here）：

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