foreach ( $units as $key = $unit ) {
    $other_units = $units;
    unset( $other_units[$key] );
    $other_units = array_values( $other_units );

    if ( isset ( $$unit ) && ! isset( $other_units[0] ) && ! isset( $other_units[1] ) )
        return $wpdb->prepare( strtoupper( $unit ) . "( $column ) $compare %d", $$unit );
}



if ( isset( $hour ) && ! isset( $minute ) && ! isset( $second ) {
    return $wpdb->prepare( "HOUR( $column ) $compare %d", $hour );
} elseif ( ! isset( $hour ) && isset( $minute ) && ! isset( $second ) {
    return $wpdb->prepare( "MINUTE( $column ) $compare %d", $minute );
} elseif ( ! isset( $hour ) && ! isset( $minute ) && isset( $second ) {
    return $wpdb->prepare( "SECOND( $column ) $compare %d", $second );
}