在MySQL中選擇WHERE子句的所有行

Question

我有兩個表：第一列有這些列：

id 
sender 
recipient 
description
date

第二列有這些列：

id
name

發件人和收件人是引用第二個表的id的外鍵。

我嘗試選擇第一個表中的所有行。

SELECT a.id, a.description, b.name as sender, b.name as recipient, a.date FROM table_A a JOIN table_B b WHERE a.sender=b.id AND a.recipient=b.id ORDER BY date DESC

但它只顯示sender = recipient的行。 如何在每行中顯示包含唯一數據的所有行？

Answer 1

使用LEFT JOIN而不是INNER JOIN

嘗試這個：

SELECT a.id, a.description, b.name AS sender, c.name AS recipient, a.date 
FROM table_A a 
LEFT JOIN table_B b ON a.sender = b.id 
LEFT JOIN table_B c ON a.recipient = c.id 
ORDER BY a.date DESC;