多表连接抛出“不是唯一的表/别名”错误

Question

下面的查询将引发一个错误：

SELECT * FROM proposal_data 
    INNER JOIN proposal_data 
     ON proposal_data_second.proposal_id = proposal_data.proposal_id 

    INNER JOIN proposal_data_second 
     ON proposal_data_third.proposal_id = proposal_data_second.proposal_id 
    INNER JOIN proposal_data_third 
     ON proposal_data_fourth.proposal_id = proposal_data_third.proposal_id 

的错误是：

#1066 - Not unique table/alias: 'proposal_data' 

我在做什么错？

Answer 1

您错误地加入了表格。

在你当前的查询您声明之前加入表：

例如取前三行

SELECT * FROM proposal_data 
    INNER JOIN proposal_data 
     ON proposal_data_second.proposal_id = proposal_data.proposal_id 

这里您声明proposal_data_second表之前proposal_data_second加盟proposal_data。

而且你并不需要使用表名peoposal_data两次：

SELECT * FROM proposal_data 
    INNER JOIN proposal_data --This is invalid syntax 

试试这个：

SELECT * FROM proposal_data 
    INNER JOIN proposal_data_second 
      ON proposal_data_second.proposal_id = proposal_data.proposal_id 
    INNER JOIN proposal_data_third 
      ON proposal_data_third.proposal_id = proposal_data_second.proposal_id 
    INNER JOIN proposal_data_fourth 
      ON proposal_data_fourth.proposal_id = proposal_data_third.proposal_id 

更多看到MySQL: JOIN Syntax