In article <m23bmff78i.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Douglas McNaught <doug@xxxxxxxxxxxx> writes:
> Rory Browne <rory.browne@xxxxxxxxx> writes:
>> select u.username, g.groupname from users u, groups g where u.group_id=g.id
>> (assuming users are in exactly one group)
>>
>> If the group_id field in the users table was corrupted, and set to a
>> value that isn't in the groups table, then that view wouldn't return
>> anything.
> That's why foreign key constraints are good. :)
Well, Rory already confessed that he came from a MySQL background :-)
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
