remove duplicates from sql union

Question

I\'m doing some basic sql on a few tables I have, using a union(rightly or wrongly)

but I need remove the duplicates. Any ideas?

select * from calls
         


        

Answer 1

Since you are still getting duplicate using only UNION I would check that:

• That they are exact duplicates. I mean, if you make a

  SELECT DISTINCT * FROM () AS subquery

  you do get fewer files?

• That you don't have already the duplicates in the first part of the query (maybe generated by the left join). As I understand it UNION it will not add to the result set rows that are already on it, but it won't remove duplicates already present in the first data set.