在MySQL中选择WHERE子句的所有行

Question

I have two tables: The First has these columns:

id 
sender 
recipient 
description
date

and the second has these columns:

id
name

and sender and recipient are foreign key that reference to id of the second table.

I try to select all rows in the first table.

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

But it shows only rows where sender = recipient. How can I show all rows with unique data in each row?

Answer 1

Use LEFT JOIN instead of INNER JOIN

Try this:

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;