From: | Hiroshi Inoue <inoue(at)tpf(dot)co(dot)jp> |
---|---|
To: | greg(dot)campbell(at)us(dot)michelin(dot)com |
Cc: | pgsql-odbc(at)postgresql(dot)org |
Subject: | Re: '= NULL' is not the same as 'IS NULL' |
Date: | 2006-09-06 23:30:41 |
Message-ID: | 44FF5A21.7030408@tpf.co.jp |
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Lists: | pgsql-odbc |
greg(dot)campbell(at)us(dot)michelin(dot)com wrote:
> I have a question for the mailing list.
> More generally, let us assume that when in Access, you change a record
> focus (after a delete, insert, update. upon opening a form, or moving the
> Access cursor), it may be reasonable to execute one or more SELECT queries
> to refresh the form.
> Why does it tend to use the WHERE clause to match each field value, instead
> of a primary key for a match? What are the conditions that force primary
> key usages vs. "match every field" syntax?
>
From ancient times it's programmers' routine work to verify if the
target record was changed
or not before updat/deleting the record. MS seems to prefer the way to
verify and update/delete
at a time and executes an update/delete query with WHERE clause to
match each field value.
If the query update/deletes exactly one row it means that both the
verification and the execution
are OK. If it update/deletes no row it probably meas that someone
changed the record somewhere.
IMHO it's a lot simpler than the way to get the record with lock and
verify the change by the
program by itself and update/delete the record.
regarsds,
Hiroshi Inoue
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