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

Hi Rob,

> So they were null,

Yes!

> and null turns out to be a seven-character blank string!?

I don't understand how that happens. Mr Tom Lane
hinted that it might be a bug in sprintf...

> Btw, you can change the displayed value of null with
> \pset null nil
> and you will seem 4+ million 'nil's in your output

That is an excellent trick/skill!

canon=# \pset null nil
Null display is "nil".
canon=#
canon=# select maf from gallo.sds_seq_reg_shw
canon-# order by maf desc
canon-# limit 10;
maf
-----
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
(10 rows)

canon=#

Regards,

Tena Sakai
tsakai(at)gallo(dot)ucsf(dot)edu

-----Original Message-----
From: Rob Sargent [mailto:robjsargent(at)gmail(dot)com]
Sent: Wed 7/1/2009 9:36 AM
To: Tena Sakai
Cc: pgsql-sql(at)postgresql(dot)org
Subject: Re: [SQL] it's not NULL, then what is it?

So they were null, and null turns out to be a seven-character blank string!?

Btw, you can change the displayed value of null with
\pset null nil
and you will seem 4+ million 'nil's in your output

Tena Sakai wrote:
>
> Hi Osvaldo,
>
> > Try:
> > SELECT count(*) FROM gallo.sds_seq_reg_shw;
> > SELECT count(*) FROM gallo.sds_seq_reg_shw WHERE maf IS NULL;
> > SELECT count(*) FROM gallo.sds_seq_reg_shw WHERE maf IS NOT NULL;
>
> > Don't use count(maf), use count(*).
>
> Indeed!
>
> canon=# SELECT count(*) FROM gallo.sds_seq_reg_shw;
> count
> ---------
> 4645647
> (1 row)
>
> canon=# SELECT count(*) FROM gallo.sds_seq_reg_shw WHERE maf IS NULL;
> count
> ---------
> 4578363
> (1 row)
>
> canon=# SELECT count(*) FROM gallo.sds_seq_reg_shw WHERE maf IS NOT
> NULL;
> count
> -------
> 67284
> (1 row)
>
> $ dc
> 4578363 67284 + p q
> 4645647
> $
>
> Many thanks, Osvald.
>
> Regards,
>
> Tena Sakai
> tsakai(at)gallo(dot)ucsf(dot)edu
>
>
>
>
> -----Original Message-----
> From: Osvaldo Kussama [mailto:osvaldo(dot)kussama(at)gmail(dot)com]
> Sent: Tue 6/30/2009 6:49 PM
> To: Tena Sakai
> Subject: Re: [SQL] it's not NULL, then what is it?
>
> 2009/6/30 Tena Sakai <tsakai(at)gallo(dot)ucsf(dot)edu>:
> > 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;
> >
>
>
> Try:
> SELECT count(*) FROM gallo.sds_seq_reg_shw;
> SELECT count(*) FROM gallo.sds_seq_reg_shw WHERE maf IS NULL;
> SELECT count(*) FROM gallo.sds_seq_reg_shw WHERE maf IS NOT NULL;
>
> Don't use count(maf), use count(*).
>
> Osvaldo
>