Question

I want to convert this query from a not in to a not exists

select id, name, cat from posts where id not in (1, 100)

how do I turn this into a not exists

Answer 1

SELECT id, 
       NAME, 
       cat 
FROM   posts p 
WHERE  NOT EXISTS (SELECT 1 
                   FROM   (SELECT 1 AS col 
                           FROM   dual 
                           UNION 
                           SELECT 100 AS col 
                           FROM   dual) a 
                   WHERE  p.id = a.col); 

Your current query is good.But still if you want it using NOT EXISTS give this a try.