带有两个引用ONE的列的SQLite查询

Question

我很难过。我正在尝试编写一个SQLite查询，其中有两个表。一个表有两列，它们都指向第二个表中的同一列。例如，

Table1
ID     Text     Sender     Recipient    
1     Hi There  1          2 
2     What?     2          1
3     Weirdo!   3          1

Table2
ID    Name     Screenname
1     Me       Me
2     Sally    Sal_gal
3     Bob      Bob

我正在尝试编写查询，我会得到以下结果，因为Table1的Sender和Recipient都指向Table2中的ID。

Results
ID       Text       Sender       Recipient
1       Hi There    Me           Sally
2       What?       Sally        Me
3       Weirdo      Bob          Me 

Answer 1

两次使用JOIN：

SELECT t1.ID, t1.Text, t2.Name AS Sender, t3.Name AS Recipient
FROM Table1 t1
JOIN Table2 t2
  ON t1.Sender = t2.ID
JOIN Table2 t3
  ON t1.Recipient = t3.ID;

的 LiveDemo

输出：

╔════╦══════════╦════════╦═══════════╗
║ ID ║   Text   ║ Sender ║ Recipient ║
╠════╬══════════╬════════╬═══════════╣
║  1 ║ Hi There ║ Me     ║ Sally     ║
║  2 ║ What?    ║ Sally  ║ Me        ║
║  3 ║ Weirdo!  ║ Bob    ║ Me        ║
╚════╩══════════╩════════╩═══════════╝

我已经说过你已经在两个表之间定义了外语。否则，您可能需要使用LEFT JOIN。