I have two tables, SystemVariables and VariableOptions. SystemVariables is
self-explanatory, and VariableOptions contains all of the possible values for
all of the variables.
VariableOptions has a foreign key, variable_id, which states which variable it
is an option for. SystemVariables has a foreign key, choice_id, which states
which option is the currently selected one.
I've gotten around the cyclic relationship using use_alter on choice_id, and
post_update on SystemVariables' choice relationship. However, I would like to
add an extra database constraint that will ensure that choice_id is valid. The
logic I need, assuming that sysVar represents a row in the SystemVariables
table, is basically:
VariableOptions[sysVar.choice_id].variable_id == sysVar.id
But I don't know how to construct this kind of constraint using SQL,
declarative, or any other method. If necessary I could just validate this at
the application level, but I'd like to have it at the database level if
possible. I'm using Postgres 9.1.
Is this possible?
Thanks,
Cameron Jackson
Engineering Intern
Air Operations
Thales Australia
Thales Australia Centre, WTC Northbank Wharf, Concourse Level,
Siddeley Street, Melbourne, VIC 3005, Australia
Tel: +61 3 8630 4591
[email protected]<mailto:[email protected]> |
www.thalesgroup.com.au<http://www.thalesgroup.com.au>
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