FK question

[Igor Kryltsov]

Hi,

What is a difference, if any, between:
_________________________________
ALTER TABLE ONLY employee_role
ADD CONSTRAINT fk_survey_id_employee_id FOREIGN KEY (survey_id,
employee_id) REFERENCES employee_survey(survey_id, employee_id) MATCH FULL
ON UPDATE C
ASCADE ON DELETE CASCADE;
__________________________________

AND
___________________________________
ALTER TABLE ONLY employee_role
ADD CONSTRAINT fk_survey_id FOREIGN KEY (survey_id) REFERENCES
employee_survey(survey_id) MATCH FULL ON UPDATE C
ASCADE ON DELETE CASCADE;

ALTER TABLE ONLY employee_role
ADD CONSTRAINT fk_employee_id FOREIGN KEY (employee_id) REFERENCES
employee_survey(employee_id) MATCH FULL ON UPDATE C
ASCADE ON DELETE CASCADE;
_____________________________________
Thank you,
Igor

[Martijn van Oosterhout]

The second will allow combinations of (survey_id,employee_id) that are
not in employee_survey as long as the individual survey_id and
employee_id's exist. Whether that's a problem or not depends on your
schema....

On Thu, Aug 26, 2004 at 04:48:12PM +1000, Igor Kryltsov wrote:

Hi,

What is a difference, if any, between:
_________________________________
ALTER TABLE ONLY employee_role
ADD CONSTRAINT fk_survey_id_employee_id FOREIGN KEY (survey_id,
employee_id) REFERENCES employee_survey(survey_id, employee_id) MATCH FULL
ON UPDATE C
ASCADE ON DELETE CASCADE;
__________________________________

AND
___________________________________
ALTER TABLE ONLY employee_role
ADD CONSTRAINT fk_survey_id FOREIGN KEY (survey_id) REFERENCES
employee_survey(survey_id) MATCH FULL ON UPDATE C
ASCADE ON DELETE CASCADE;

ALTER TABLE ONLY employee_role
ADD CONSTRAINT fk_employee_id FOREIGN KEY (employee_id) REFERENCES
employee_survey(employee_id) MATCH FULL ON UPDATE C
ASCADE ON DELETE CASCADE;
_____________________________________


Thank you,


Igor



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