选择与查询返回的结果相反的结果

Question

I am trying to simplify my code.

I currently have two querys: one selecting the list of information and outputing it with select boxes to add to a users subscriptions then a second query to select the items that user already has subscribed but I am trying to simplify the code to one query.

I can currently get the code to display the options that the user has subscribed to with check boxes but not the opposite is there a way to select the opposite to the results in a WHERE clause?

$selectionQuery = 'SELECT t1.subId, t1.subTitle FROM tbl_subs t1 LEFT JOIN tbl_list t2 ON t2.subId = t1.subId WHERE t2.userId = '.$id.' AND t1.subId = t2.subId'; 

Answer 1

You already joining the subId at the LEFT JOIN part. Remove the AND t1.subId = t2.subId' from the WHERE part, as it joins again your resultset and overcomes the left join.

Correct:

$selectionQuery = 'SELECT t1.subId, t1.subTitle FROM tbl_subs t1 LEFT JOIN tbl_list t2 ON t2.subId = t1.subId WHERE t2.userId = '.$id.'; 

Answer 2

This code maybe is not ansiSQL but it works perfect on MYSQL.

$selectionQuery = 'SELECT t1.subId, t1.subTitle FROM tbl_subs as t1 WHERE not exists (select 1 from tbl_list as t2 where t2.userId = '.$id.' AND t1.subId = t2.subId)';