Question

I have a query that returns a bunch of information and using a join to join two tables and it works perfectly fine.

But I have a field called tickets which I need to see if there is a time available and if there is even one set it to 1 otherwise set it to 0. So like this.

SELECT 
name,poster,sid,tickets = (IF SELECT id FROM times WHERE shows.tid=times.tid LIMIT 1, 
if value returned set to 1, otherwise set to 0) 
FROM shows JOIN show_info ON (id) WHERE sid=54 order by name ASC

Obviously that is not a correct MySQL statement, but it would give an example of what I am looking for.

Is this possible? Or do I need to do the first select then for a loop through results and do the second select and set value that way? Or is one better performance wise?

Answer 1

I would look at EXISTS it is in most of the cases much faster then to COUNT all the items that matches your where statement. With that said. You query should look something like this:

SELECT 
  name,
  poster,
  sid,
  (
   CASE WHEN EXISTS(SELECT NULL FROM times WHERE shows.tid=times.tid)
      THEN 1 
      ELSE 0
   END 
  )AS tickets 
FROM 
  shows 
  JOIN show_info ON (id) WHERE sid=54 order by name ASC