Help with SQL

[maximux1]

Can anyone help me with what is wrong with this query?

$db->query_first('SELECT userid, usergroupid, membergroupids, username, password, salt FROM user WHERE (username = "$username")')

I'm getting the following error from my script -

Invalid SQL:
SELECT userid, usergroupid, membergroupids, username, password, salt FROM user WHERE username = interpolated_username;

MySQL Error : Unknown column 'interpolated_username' in 'where clause'

Thanks guys,

Max