Re: COUNT and GROUP BY performing strangely - Mailing list pgsql-novice

http://stackoverflow.com/questions/2054235/why-doesnt-postgres-group-by-null-select-counts

http://www.postgresql.org/docs/9.0/static/functions-aggregate.html

says "number of input rows for which the value ofexpression is not null"

On Fri, Oct 25, 2013 at 3:38 PM, James David Smith <james.david.smith@gmail.com> wrote:

Hi everyone,

Any thoughts on the below three queries please?

james_traffic=# SELECT  count(*) FROM stage;
 count
--------
 430991
(1 row)

james_traffic=# SELECT bad_flag, count(bad_flag) FROM stage GROUP BY bad_flag;
 bad_flag | count
----------+-------
           |     0
        1 |  4102
(2 rows)

james_traffic=# SELECT count(bad_flag) FROM stage;
 count
-------
  4102
(1 row)

 I'm confused as to why the second query doesn't return this:

 bad_flag  | count
--------------+-------
               | 426889
        1     |  4102

It should count the records surely, even if the field is blank/null ?

Thanks

James


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