Question

I am running an SQL statement:

$sql = "SELECT pic, userid 
        FROM user_details 
          INNER JOIN wp_users ON user_details.userid  
        WHERE wp_users.id = user_details.userid 
        LIMIT $recordstart, $pagesize
       ";

The query is meant to select records from user_details and wp_users, but should only select if there is a match (wp_users.id = user_details.userid).

The target is for it to basically select from a table while retrieving a record (based on the id match) from the other table

The problem is that it shows duplicate records. How can I fix this problem?

Answer 1

You should put your JOIN condition after ON. Like this:

$sql="select pic, userid 
      from user_details 
      inner join wp_users on (wp_users.id=user_details.userid)
      limit $recordstart, $pagesize";

But the real problem is that you have more then 1 record in user_details for each corresponding record in wp_users (or vise versa).
INNER JOIN is causing database to make a Cartesian product of user_details and wp_users records. Then result table is filtered by your current WHERE condition (wp_users.id=user_details.userid). Depends on your needs you can use GROUP BY or DISTINCT if you want to retrieve unique records only.
For example, if you need userid to be unique:

$sql="select pic, userid 
      from user_details 
      inner join wp_users on (wp_users.id=user_details.userid)
      group by userid
      limit $recordstart, $pagesize";