| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | Matt Zagrabelny <mzagrabe(at)d(dot)umn(dot)edu> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Rob Sargent <robjsargent(at)gmail(dot)com>, "pgsql-generallists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: count(*) vs count(id) |
| Date: | 2021-02-02 01:16:50 |
| Message-ID: | CAKFQuwa2ki4CyncgrMWqR8aewxfhPjtXX4fy+89yrWsDms+Upg@mail.gmail.com |
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| Lists: | pgsql-general |
On Mon, Feb 1, 2021 at 6:14 PM Matt Zagrabelny <mzagrabe(at)d(dot)umn(dot)edu> wrote:
> Which field is count(*) counting if it is counting nulls?
>
count(id) excludes from the count rows where the id field is null. The
presence of a left join in your query is introducing a null here due to
there not being a related field, not because the id value in a table is
actually null.
David J.
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