Question

i have this query,

$query = 'SELECT * FROM users where id ="'.$_SESSION['user_id'].'"'; 

My problem is that i don’t know how to left join it with another table..using another where or “On” clause..

can you please help me with the syntax of this?

It should be something like SELECT $query FROM users,retailer ON $query.user_id=retailer.user_id
….

"SELECT users.first_name, retailer.date
FROM users AS users
LEFT JOIN retailer AS retailer ON users.user_id=retailer.user_id
WHERE users.user_id=" . $_SESSION['user_id']

Thanks!

Answer 1

LEFT JOIN is pretty simple

For your example:

$query = "SELECT u.*, r.*
FROM users AS u
LEFT JOIN retailer AS r ON u.user_id=r.user_id
WHERE u.user_id=" . $_SESSION['user_id']

“AS” keyword creates alias so there is no need of making alias “users” of table “users”.

Secondly, LEFT JOIN is useful if there is a chance that second table contains no matches to first one yet you still need that attribute to show – attributes of second table will have NULL values if no matches found.

I’m not really sure you need a LEFT JOIN in your query.