|Subject||Re: [firebird-support] Foreign key different field type|
On Mon, Jun 19, 2017 at 1:21 PM, Thomas Steinmaurer ts@... [firebird-support] <firstname.lastname@example.org> wrote:,
> Can someone show me example when it is usefull to have different field
> type in [referenced and referencing keys of a foreign key relationship]?
> Why this is not forbidden?Why should it be forbidden? Not everything that's dumb is disallowed.
Perhaps cause the referenced column in table test1 can only store a
subset (SMALLINT) of the value range of the INTEGER used in test2?
Even if this works at DDL time, I wonder how strict the optimizer then
is in JOIN statements using an index. Haven't tried.Nor have I tried, but Firebird uses the same key representation for most numericcolumns, so having mixed sizes of numbers - or different scales - in a foreign keyshouldn't matter to the optimizer. The exception - which may have been changed -was the representation of int64. Having a single key format for numbers makesit simple to increase the size of columns or change the scale.Good luck,Ann