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

Hi Steve,

> I believe count will only count not-null anyway
> so this will always return zero.

Understood. But that doesn't help me...
What I need is a query expression that I can substitute
for isblabla below:

select maf
from gallo.sds_seq_reg_shw
where maf isblabla;

Regards,

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

-----Original Message-----
From: Steve Crawford [mailto:scrawford(at)pinpointresearch(dot)com]
Sent: Tue 6/30/2009 3:39 PM
To: Tena Sakai
Cc: pgsql-sql(at)postgresql(dot)org
Subject: Re: [SQL] it's not NULL, then what is it?

...
>
>
> canon=# select count(maf) from gallo.sds_seq_reg_shw
> canon-# where maf ISNULL;
> count
> -------
> 0
> (1 row)
>
I believe count will only count not-null anyway so this will always
return zero. Try count(*) instead of count(maf). Here's an example:

steve(at)[local]=> select * from barr;
LOG: duration: 0.226 ms
a | b
---+---
a | b
c | d
| e
(3 rows)

steve(at)[local]=> select coalesce(a, 'a is null'), coalesce(b, 'b is
null') from barr;
LOG: duration: 0.283 ms
coalesce | coalesce
-----------+----------
a | b
c | d
a is null | e
(3 rows)

steve(at)[local]=> select count(a) from barr;
LOG: duration: 0.339 ms
count
-------
2
(1 row)

steve(at)[local]=> select count(*) from barr where a isnull;
LOG: duration: 0.350 ms
count
-------
1
(1 row)