mysql - 如何将一列内连接到两个不同的列？

Question

我有两个表:

**projects**

|Equity_holders| Financer  |
|--------------|-----------|
|Company 1     | Company 7 |
|Company 2     | Company 9 |
|Company 3     | Company 4 |

**entities**

|name         | country |
|-------------|---------|
|Company 1    |  USA    |
|Company 2    |  Italy  |
|Company 3    |  UK     |
|Company 4    |  Nigeria|
|Company 5    |  Brazil |
|Company 6    |  China  |
|Company 7    |  France |
|Company 8    |  China  |
|Company 9    |  Germany|

我希望我的显示表看起来像:

|Equity_holders| country |Financer     | country |
|--------------|---------|-------------|---------|
|Company 1     |  USA    |Company 4    |  Nigeria|
|Company 2     |  Italy  |Company 7    |  France |
|Company 3     |  UK     |Company 9    |  Germany|                       

我已成功使用 INNER JOIN 将“股权持有人”列与实体名称进行匹配并显示相应的“国家/地区”:

SELECT projects.Equity_holders,entities.country, projects.Financer,entities.country
FROM projects
INNER JOIN entities ON projects.Equity_holders LIKE CONCAT('%', entities.name, '%')
INNER JOIN entities A ON projects.Financer LIKE CONCAT('%', entities.name, '%' )

但无法让“Financer”列显示正确的对应国家/地区。它只是复制“Equity_Holders”列。我感觉选择查询有问题，但不知道要更改什么。

Answer 1

您可以尝试以下操作 - 您需要将第二个实体别名为 e1 并使用 e1.country 作为country1

SELECT projects.Equity_holders,entities.country, projects.Financer,e1.country
FROM projects
INNER JOIN entities ON projects.Equity_holders=entities.name
INNER JOIN entities e1 ON projects.Financer=e1.name