Question

I have this query here:

  $query='insert into pageview (visitor,id_realestate,time)
  select "q17872745t", 150, now() 
     from pageview a
     where DATE_ADD(now(),INTERVAL -30 MINUTE) > (
        select max(time) from pageview b where a.id_realestate=b.id_realestate AND a.visitor=b.visitor
  ) LIMIT 1';

I want this part:

  select max(time) from pageview b where a.id_realestate=b.id_realestate AND a.visitor=b.visitor

to return a date/time which is now() minus 40 minutes if there are no results

Answer 1

Wrap the MAX(time) in an IFNULL clause.

IFNULL(MAX(time), NOW() - INTERVAL 40 MINUTE)