Question

I need a query which will get number of downloads for file. Table is like this

fid  uid        ip
21    0      111.111.111.11
21    0      222.222.222.22
21    0      111.111.111.11
21    1      333.333.333.33
21    1      111.111.111.11
21    1      444.444.444.44
21    2      555.555.555.55
22    0      111.111.111.11

uid is user id and if it’s 0 user is anonymous.
Query should count number of rows where fid is 21, but with distinct values of ips if users are anonymous and distinct values of users AND ips if they are registered.( If user download a file, logs out, and download again as anonymous, query should count this as 1 download)

In this example, query should count something like this

fid  uid        ip
21    0      111.111.111.11
21    0      222.222.222.22
21    1      333.333.333.33
21    2      555.555.555.55

and result should be 4.

Any help is much appreciated.

EDIT: I strikethrough some description, because it’s confusing.
Thanks for all the comments and possible solutions.

Answer 1

This query gets the grouping you want, except that I don’t know the business rule that determined 333.333.333.33 should be returned for uid=1. I opted to use MAX(ip) instead:

select distinct t.uid, t.ip
from MyTable t
inner join (
  select uid, max(ip) maxip
  from MyTable
  where fid = 21
  group by uid
) tm on t.uid = tm.uid
and ((t.uid <> 0 and t.ip = tm.maxip) or t.uid = 0)
where t.fid = 21

SQL Fiddle Example #1

You can then wrap it in a count, like this:

select count(*)
from (
  select distinct t.uid, t.ip
  from MyTable t
  inner join (
    select uid, max(ip) maxip
    from MyTable
    where fid = 21
    group by uid
  ) tm on t.uid = tm.uid
  and ((t.uid <> 0 and t.ip = tm.maxip) or t.uid = 0)
  where t.fid = 21
) a

SQL Fiddle Example #2