Re: it's not NULL, then what is it? - Mailing list pgsql-sql

Just out of curiosity did you try maf = 0?

Hi Everybody,

I have a table called gallo.sds_seq_reg_shw,
which is like:

  canon=# \d gallo.sds_seq_reg_shw
       Table "gallo.sds_seq_reg_shw"
        Column      |  Type   | Modifiers
  ------------------+---------+-----------
   name             | text    |
   response         | text    |
   n                | integer |
   source           | text    |
   test             | text    |
   ref              | text    |
   value            | real    |
   pvalue.term      | real    |
   stars.term       | text    |
   gtclass.test     | text    |
   fclass.test      | text    |
   gtclass.ref      | text    |
   fclass.ref       | text    |
   markerid         | integer |
   maf              | real    |
   chromosome       | text    |
   physicalposition | integer |
   id               | text    |
   ctrast           | text    |
 
I am intereseted in the column maf (which is real):

  canon=# select maf from gallo.sds_seq_reg_shw
  canon-#  order by maf asc;
       maf    
  -------------
   0.000659631
   0.000659631
   0.000659631
   0.000659631
        .
  (trunacated for the interest of breivity)
        .

Another way to look at this column is:

  canon=# select maf from gallo.sds_seq_reg_shw
  canon-#  order by maf desc;
       maf    
  -------------
             
             
             
        .
  (trunacated for the interest of breivity)
        .

These rows shown are blanks, as far as I can tell.
But...

  canon=# select count(maf) from gallo.sds_seq_reg_shw;
   count
  -------
   67284
  (1 row)
 
  canon=# select count(maf) from gallo.sds_seq_reg_shw
  canon-#  where maf ISNULL;
   count
  -------
       0
  (1 row)
 
  canon=#
  canon=# select count(maf) from gallo.sds_seq_reg_shw
  canon-#  where maf NOTNULL;
   count
  -------
   67284
  (1 row)

My confusion is that if they are real and not null,
what are they?  How would I construct a query to do
something like:

 select count(maf)
   from gallo.sds_seq_reg_shw
  where maf ISBLANK;

Thank you in advance.

Regards,

Tena Sakai
tsakai@gallo.ucsf.edu