[SQL] a bit confused about distinct() function

[Tena Sakai]

Hi Everybody,

I am a bit confused about distinct() function.

I wrote a simple query like this:

 select subjectid, markerid, allele1id, allele2id
  from tsakai.mygenotype2
 where subjectid in (53684, 53688, 53699, 53700, 53704, 53705, 53713, 53714, 
53716, 53724)
       and
       markerid in  (1259501, 1259504, 1260210, 1260211, 1260212, 1260214, 
1260215, 1260238, 1260248, 1260562)
 order
    by subjectid;

Here's what I got back:

  subjectid | markerid | allele1id | allele2id
 -----------+----------+-----------+-----------
      53684 |  1260214 |   2521543 |   2521543
      53684 |  1260214 |   2521543 |   2521543
      53684 |  1260215 |   2521537 |   2521538
      53688 |  1260562 |   2522243 |   2522243
      53688 |  1260562 |   2522243 |   2522243
      53699 |  1260562 |   2522243 |   2522243
      53699 |  1260214 |   2521543 |   2521544
      53699 |  1260214 |   2521543 |   2521544
      53704 |  1260215 |   2521537 |   2521537
      53714 |  1260214 |   2521543 |   2521543
 (10 rows)

Which is good, but seeing the duplicate rows in result
made me want to write:

 select distinct (subjectid, markerid, allele1id, allele2id)
   from tsakai.mygenotype2
  where subjectid in (53684, 53688, 53699, 53700, 53704, 53705, 53713, 53714, 
53716, 53724)
        and
        markerid in  (1259501, 1259504, 1260210, 1260211, 1260212, 1260214, 
1260215, 1260238, 1260248, 1260562)
  order
     by subjectid;

and what I got back was:
 ERROR:  could not identify an ordering operator for type record
 HINT:  Use an explicit ordering operator or modify the query.

Could somebody give me a tip as to what I could do
to get what I want?  Ie., I want get back is:

  subjectid | markerid | allele1id | allele2id
 -----------+----------+-----------+-----------
      53684 |  1260214 |   2521543 |   2521543
      53684 |  1260215 |   2521537 |   2521538
      53688 |  1260562 |   2522243 |   2522243
      53699 |  1260562 |   2522243 |   2522243
      53699 |  1260214 |   2521543 |   2521544
      53704 |  1260215 |   2521537 |   2521537
      53714 |  1260214 |   2521543 |   2521543

Regards,

Tena Sakai
tsa...@gallo.ucsf.edu