我在这个查询中做错了什么？

Question

There are three tables,

• storing user details
• storing groups details
• storing user and group ids.

I need to check if a user is already a member of one group. I'm using this query to achieve that:

SELECT u.id, g.id 
FROM users u, groups g 
INNER JOIN user_groups ug 
ON ug.user_id = u.id AND ug.group_id = g.id 
WHERE ug.user_id = ? AND ug.group_id = ?

but this is throwing me an error:

Call to a member function bind_param() on boolean in

I have checked if i have misspelled some word in my query and everything is okay.

EDIT:

Here is a function:

public function isUserMember($user_id, $group_id) {
        $stmt = $this->conn->prepare("
            SELECT u.id, g.id from users u, groups g 
            INNER JOIN user_groups ug 
            ON ug.user_id = u.id AND ug.group_id = g.id 
            WHERE ug.user_id = ? AND ug.group_id = ?");
        $stmt->bind_param("ii", $user_id, $group_id); // here i'm getting an error
        $stmt->execute();
        $stmt->store_result();
        $num_rows = $stmt->num_rows;
        $stmt->close();
        return $num_rows > 0;
}

Answer 1

Try following changes

removed unnecessary join with user table because if you have user_id and group_id you don't need to join it with user

SELECT ug.id, g.id 
from  user_groups ug  
inner join  groups g 
on ug.group_id = g.id 
WHERE ug.user_id = ? AND ug.group_id = ?