如何在另一个表中执行的mysql查询中添加条件？

Question

I develope a website for E-books, i have in database table for authors and table for publishers .. sometimes the author name is added also in publishers table as a publisher Now i have his name as an author and a publisher .. when i search in the site for his name, it return twice because i search in authors table and in publishers table then merge two queries

this is my code :-

function generate_results($keyword, $row = 0) {


        $result1 = $this->db->query("SELECT au_id,au_name,au_state,SUBSTR(au_info,1,190) AS au_info,au_img FROM d_author where (au_name LIKE '%$keyword%' or au_info LIKE '%$keyword%') and au_state = '1' limit $row,20");


        $result2 = $this->db->query("SELECT pub_id,pub_name,pub_state,SUBSTR(pub_info,1,190) AS pub_info,pub_img FROM d_publishing where (pub_name LIKE '%$keyword%' or pub_info LIKE '%$keyword%') and and pub_state = '1' limit $row,20");


        $results = array_merge($result1->result_array(), $result2->result_array());

        return $results;
    }  

Now i want to modify the second query to something like that : select all publishers from "publishers table" where the name of publisher is like $keyword and this $keyword doesn't exist in authors table .. I mean if this name exist in authors don't select it in publishers How can i translate that meaning to Mysql Query

Answer 1

First, check out sql-injections before continuing to develop in your ebook-application. Looks like your keyword is not checked to be a safe parameter. And just to be sure, do you know about csrf and xss? If not, check about that too. This is very important.

Secondaly, you should consider working on your database design to avoid having duplicated values . Check out "database normalization" for more information. Seems like you could do another table to extract your "contact information" like name, state, id etc. This would make it possible for your author-table and publisher-table to use a "contact_id" referencing the contact-information-table.

Last but not least, to answer your question, you can generelly solve such problems with an "anti join". Use a left join on the authors table in the second query and check for "IS NULL" on matches with the publisher table. More information here: http://explainextended.com/2009/09/18/not-in-vs-not-exists-vs-left-join-is-null-mysql/

I do not know if I understand your database design completly right, but it also seems like an UNION combined with a DISTINCT could help you - and you wouldn't even need this array_merge -stuff. I would suggest you to check out these two commands in the mysql docs.