$query = $wpdb->prepare(
    "SELECT  {$columns_select}
    FROM {$wpdb->comments} _question
            INNER JOIN {$wpdb->posts} _course
                    ON _question.comment_post_ID = _course.ID
            INNER JOIN {$wpdb->users} _user
                    ON _question.user_id = _user.ID
            LEFT JOIN {$wpdb->commentmeta} _meta
                    ON _question.comment_ID = _meta.comment_id
            LEFT JOIN {$wpdb->commentmeta} _meta_archive
                    ON _question.comment_ID = _meta_archive.comment_id
    WHERE   _question.comment_type = 'tutor_q_and_a'
            AND _question.comment_parent = 0
            AND _question.comment_content LIKE %s
            {$in_course_id_query}
            {$question_clause}
            {$meta_clause}
            {$qna_types_caluse}
            {$filter_clause}
    {$order_condition}
    {$limit_offset}",
    $search_term
);