@Agelios I tried adding select to both queries, but it only works when I select 1 column. When I select 2 or more columns, the error showed up again.
@biishmar Like I said, it is working fine if I remove the
$first = Professionals::SomeConditions
$second = Professional::SomeConditions
->union($first) <<<--- If i remove this, everything is working fine.
$first = I'm trying to get only the featured professional where featured_date >= today.
$second = I'm trying to get the latest professional and combining the result with $first.