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From: Len Morgan <[email protected]>
To: Alexander Turchin <[email protected]>
To: PostgreSQL Mailing List <[email protected]>
Subject: Re: COUNTs don't add up
Date: Mon, 23 Jul 2001 15:37:55 -0500
Message-ID: <[email protected]> (raw)
References: <[email protected]>

Could there be two rows that have NULL is the value?  They don't "count" as
far as I know.  You can try:

SELECT count(*) from homol_loclink WHERE species2 IS NULL

to verify this.

len morgan

----- Original Message -----
From: "Alexander Turchin" <[email protected]>
To: "PostgreSQL Mailing List" <[email protected]>
Sent: Monday, July 23, 2001 2:32 PM
Subject: [GENERAL] COUNTs don't add up


> Hello all,
>
> I have a database where (I believe; the database was not made by me) one
> of the columns contains only two values: A or B. When I count all the
> rows in the database I get X; when I count the rows containing A or B in
> that column I get X-2; when I count the rows containing neither A nor B
> I get 0. Any explanation (hopefully, again, I am doing something wrong
> :)?
>
> The actual queries are found below.
>
> Thanks!
>
> Alex
>
> aturchin=# SELECT COUNT(*) FROM homol_loclink
> aturchin-# WHERE (species2 = 'Mus musculus') OR
> aturchin-# (species2 = 'Rattus norvegicus');
>  count
> -------
>   7110
> (1 row)
>
> aturchin=# SELECT COUNT(*) FROM homol_loclink;
>  count
> -------
>   7112
> (1 row)
>
> aturchin=# SELECT COUNT(*) FROM homol_loclink
> aturchin-# WHERE (species2 <> 'Mus musculus') AND
> aturchin-# (species2 <> 'Rattus norvegicus');
>  count
> -------
>      0
> (1 row)
>
>
>
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