Just a simple idea (taking that your field names contain no underscores (for bravity, you can change this approach to fit your task)):

my %AS = (
 requests_id => 'requests.id AS requests_id',
 requests_name => 'requests.name AS requests_name',
 requests_rating => '(select count(*) from ratings where ....) AS requ
+ests_rating',
 ...etc...
);

my $sth = $dbh->prepare( qq|SELECT
    $AS{request_id}, $AS{request_name}, $AS{request_rating},
    ...etc
);
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This also allows expand your SELECTs in future without touching code logic.