Re: '= NULL' is not the same as 'IS NULL'

greg.campbell@us.michelin.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