如何在许多表中使用关键字进行搜索

>我的数据库书中有三个表，作者，出版...我希望用户可以搜索三个表，如果他写任何相关的单词。如果在书表中找不到相同的单词，它将在另一个表中搜索，依此类推......我这样做，但有些事情出错，我希望它在一个 MySQL 句子中。有人请帮我

function getsomeword($keyword) {
    $result1 = $this->db->query("SELECT bo_id,bo_name,bo_state,bo_about FROM d_book where (bo_name like '%$keyword%' or bo_about like '%$keyword%') and bo_state = '1'");
    $result1 = $result1->num_rows();
    $result2 = $this->db->query("SELECT au_id,au_name,au_state,au_info FROM d_author where (au_name like '%$keyword%' or au_info like '%$keyword%') and au_state = '1'");
    $result2 = $result2->num_rows();
    $result3 = $this->db->query("SELECT pub_id,pub_name,pub_state,pub_info FROM d_publishing where (pub_name like '%$keyword%' or pub_info like '%$keyword%') and pub_state = '1'");
    $result3 = $result3->num_rows();
    return $result1 + $result2 + $result3;
}