Re: it's not NULL, then what is it?

<p><font size="2">Hi Edward,<br /><br /> > Just out of curiosity did you try maf = 0?<br /><br /> Yes, and this is
whatI get:<br /><br />   canon=# select maf<br />   canon-#   from gallo.sds_seq_reg_shw<br />   canon-#  where maf =
0;<br/>    maf<br />   -----<br />   (0 rows)<br /><br /> Regards,<br /><br /> Tena Sakai<br />
tsakai@gallo.ucsf.edu<br/><br /><br /> -----Original Message-----<br /> From: pgsql-sql-owner@postgresql.org on behalf
ofEdward W. Rouse<br /> Sent: Tue 6/30/2009 3:22 PM<br /> To: pgsql-sql@postgresql.org<br /> Subject: Re: [SQL] it's
notNULL, then what is it?<br /><br /> Just out of curiosity did you try maf = 0?<br /><br /><br /><br /> Edward W.
Rouse<br/><br /><br /><br /> From: pgsql-sql-owner@postgresql.org [<a
href="mailto:pgsql-sql-owner@postgresql.org">mailto:pgsql-sql-owner@postgresql.org</a>]<br/> On Behalf Of Tena Sakai<br
/>Sent: Tuesday, June 30, 2009 6:03 PM<br /> To: pgsql-sql@postgresql.org<br /> Subject: [SQL] it's not NULL, then what
isit?<br /><br /><br /><br /> Hi Everybody,<br /><br /> I have a table called gallo.sds_seq_reg_shw,<br /> which is
like:<br/><br />   canon=# \d gallo.sds_seq_reg_shw<br />        Table "gallo.sds_seq_reg_shw"<br />        
Column     |  Type   | Modifiers<br />   ------------------+---------+-----------<br />    name             | text   
|<br/>    response         | text    |<br />    n                | integer |<br />    source           | text    |<br
/>   test             | text    |<br />    ref              | text    |<br />    value            | real    |<br />   
pvalue.term     | real    |<br />    stars.term       | text    |<br />    gtclass.test     | text    |<br />   
fclass.test     | text    |<br />    gtclass.ref      | text    |<br />    fclass.ref       | text    |<br />   
markerid        | integer |<br />    maf              | real    |<br />    chromosome       | text    |<br />   
physicalposition| integer |<br />    id               | text    |<br />    ctrast           | text    |<br /><br /> I
amintereseted in the column maf (which is real):<br /><br />   canon=# select maf from gallo.sds_seq_reg_shw<br />  
canon-# order by maf asc;<br />        maf   <br />   -------------<br />    0.000659631<br />    0.000659631<br />   
0.000659631<br/>    0.000659631<br />         .<br />   (trunacated for the interest of breivity)<br />         .<br
/><br/> Another way to look at this column is:<br /><br />   canon=# select maf from gallo.sds_seq_reg_shw<br />  
canon-# order by maf desc;<br />        maf   <br />   -------------<br />             <br />             <br />
            <br/>         .<br />   (trunacated for the interest of breivity)<br />         .<br /><br /> These rows
shownare blanks, as far as I can tell.<br /> But...<br /><br />   canon=# select count(maf) from
gallo.sds_seq_reg_shw;<br/>    count<br />   -------<br />    67284<br />   (1 row)<br /><br />   canon=# select
count(maf)from gallo.sds_seq_reg_shw<br />   canon-#  where maf ISNULL;<br />    count<br />   -------<br />       
0<br/>   (1 row)<br /><br />   canon=#<br />   canon=# select count(maf) from gallo.sds_seq_reg_shw<br />   canon-# 
wheremaf NOTNULL;<br />    count<br />   -------<br />    67284<br />   (1 row)<br /><br /> My confusion is that if
theyare real and not null,<br /> what are they?  How would I construct a query to do<br /> something like:<br /><br />
 selectcount(maf)<br />    from gallo.sds_seq_reg_shw<br />   where maf ISBLANK;<br /><br /> Thank you in advance.<br
/><br/> Regards,<br /><br /> Tena Sakai<br /> tsakai@gallo.ucsf.edu<br /><br /><br /></font>