Hello,
I'm having a problem using foreign keys, or at least in a way i find good. Basicly I have a table I wish to use as a
foreignkey with lookup "id" and "code", like:
1,a
1,b
1,c
2,a
2,d
I have of course an UNIQUE on (id,code). However, in the table I want the key to apply to, I only have one column that
Iwant to restrict to one lookup. Basicly I want to do something like:
ALTER TABLE data ADD FOREIGN KEY ( 2, col ) REFERENCES lookups ( id, code )
In this case 2 is a literal integer, not a column reference and the result should be that a and d is legal - but this
commandisn't legal.
Options:
1) Add another column to my data table like:
ALTER TABLE data ADD COLUMN dummy INTEGER DEFAULT 2
ALTER TABLE data ADD FOREIGN KEY ( dummy, col ) REFERENCES lookups ( id, code )
This works, but creates a useless column in my data table that feels very unclean.
2) Refactor the lookup table to have one lookup per table. However, this also means I'll probably need to duplicate
translationtables, value mapping tables etc. and a bunch of queries would have to dynamically alter table names. It
seemsmore than a little messy.
3) Forego integrity checking in the database and do it in the app. However, I sense trouble with that apporach in the
futureas I hope several app boxes can do work on the same database.
4) Trigger? Something else?
The way I'd like to do it seems like the cleanest, if only it'd work. Why can't the foreign key evaluate the literal,
inthe same way it could in a query? It's possible that I'm way outside all SQL standards now but it seems like sensible
functionalityto me.
Regards,
Kjell Rune
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