I am not sure of the objective.
In general, an SQL query should get the result.
There is probably some syntax error below, but
this is the general idea.

while ( ($dumb, $guru) = ( ($sth->fetchrow)[0,4]) )
{
     #do something here....with $dumb and $guru... 
     #maybe push [$dumb,$guru] to another array?
     #but that could be just another SQL query.
}
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