| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | Rich Shepard <rshepard(at)appl-ecosys(dot)com> |
| Cc: | "pgsql-generallists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Refining query statement |
| Date: | 2019-01-17 16:36:53 |
| Message-ID: | CAKFQuwZFgogSc1Td0hXz7Jtzn3YvFisDEnPL6+3NLO1O7hsnkA@mail.gmail.com |
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| Lists: | pgsql-general |
On Thu, Jan 17, 2019 at 9:14 AM Rich Shepard <rshepard(at)appl-ecosys(dot)com> wrote:
> ORDER BY c.contact_id, a.next_contact DESC;
> The WHERE clause needs to exclude a contact_id where the most current row in
> Activities has NULL for the next_contact column.
Why is next_contact allowed to be null?
Your concept of "most current row" is strictly based upon next_contact
so if next_contact is null it is impossible to know whether it is the
most current row (consider that two activities could be missing the
next_contact date - which of those is the most current?)
David J.
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