如何从已知和未知作者的帖子表中获取帖子

Question

I have a posts table in sql which its author column is connected to users table. I use a single sql query to get post from posts table and the author's name from users table. My posts table looks like this:

+----+-----------------+-----------------+--------+
| id | title           | label           | author |
+----+-----------------+-----------------+--------+
| 22 | Post 1          | post-1          |      2 |
| 24 | Post 2          | post-2          |      4 |
| 25 | Post 3          | post-3          |      4 |
| 26 | Post 4          | post-4          |      5 |
| 27 | Post 5          | post-5          |      6 |
| 28 | Post 6          | post-6          |      2 |
| 29 | Post 7          | post-7          |      2 |
| 30 | Post 8          | post-8          |      2 |
| 32 | Post 9          | post-9          |      2 |
+----+-----------------+-----------------+--------+

I use this sql query to get post title, label and its authors name and surname.

SELECT `posts`.id, `posts`.title, `posts`.label, users.id AS author, users.name AS name, users.surname AS surname
FROM `posts`
INNER JOIN users
ON users.id = posts.author
ORDER BY `date` DESC;

This works perfectly fine but it only returns posts with known authors which is id 2 because in users table I only have author id 2. Other authors (4, 5 and 6) are missing. So instead of not showing the posts with unknown authors, I want to show them null as its name and surname variable. By the way the result is;

+----+----------------+----------------+--------+------+---------+
| id | title          | label          | author | name | surname |
+----+----------------+----------------+--------+------+---------+
| 32 | Post 9         | post-9         |      2 | Jack | Smith   |
| 30 | Post 8         | post-8         |      2 | Jack | Smith   |
| 29 | Post 7         | post-7         |      2 | Jack | Smith   |
| 28 | Post 6         | post-6         |      2 | Jack | Smith   |
| 22 | Post 1         | post-1         |      2 | Jack | Smith   |
+----+----------------+----------------+--------+------+---------+

Answer 1

Instead of INNER JOIN you have to use LEFT JOIN. The result of an inner join just shows entities which are represented in both tables. A left join adds a null value, when an entity is represented in the first table but not in the second.

Answer 2

Try to use left Join :

one more this create the foreign key constrain while refer another table value.

SELECT `posts`.id, `posts`.title, `posts`.label, posts.id AS author, 
  users.name AS name, users.surname AS surname
    FROM `posts`
       LEFT JOIN users
          ON users.id = posts.author
             ORDER BY `date` DESC;