Question

I have two tables: “users” and “posts.” The posts table has a ‘post’ column and a ‘poster_id’ column. I’m working on a PHP page that shows the latest posts by everyone, like this:

SELECT * FROM posts WHERE id < '$whatever' LIMIT 10

This way, I can print each result like this:

id: 43, poster_id:'4', post: hello, world
id: 44, poster_id:'4', post: hello, ward
id: 45, poster_id:'5', post: oh hi!
etc...

Instead of the id, I would like to display the NAME of the poster (there’s a column for it in the ‘users’ table)

I’ve tried the following:

SELECT * 
FROM posts 
WHERE id < '$whatever' 
       INNER JOIN users 
           ON posts.poster_id = users.id LIMIT 10

Is this the correct type of join for this task? Before learning about joins, I would query the users table for each post result. The result should end up looking similar to this:

id: 43, poster_id:'4', name:'foo', post: hello, world
id: 44, poster_id:'4', name:'foo', post: hello, ward
id: 45, poster_id:'5', name:'fee', post: oh hi!
etc...

Thanks for helping in advance.

Answer 1

WHERE clause must come after the FROM clause.

SELECT  posts.*, users.*   // select your desired columns
FROM    posts 
        INNER JOIN users ON posts.poster_id = users.id 
WHERE   id < '$whatever'
LIMIT   10

the SQL Order of Operation is as follows:

• FROM clause
• WHERE clause
• GROUP BY clause
• HAVING clause
• SELECT clause
• ORDER BY clause

UPDATE 1

For those column names that exists on both tables, add an ALIAS on them so it can be uniquely identified. example,

SELECT  post.colName as PostCol, 
        users.colName as UserCol, ....
FROM ....

on the example above, both tables has column name colName. In order to get them both, you need to add alias on them so in your front end, use PostCol and UserCol to get their values.