On Jan 8, 2012, at 9:33, Phoenix Kiula phoenix.ki...@gmail.com wrote:
Hi. Hope I'm articulating the question correctly.
I currently have a foreign key like this:
fk_table2 FOREIGN KEY (id) REFERENCES table1(id) ON DELETE CASCADE;
Given the peculiar needs of this db, it seems that in some cases we
will need to track the id of table2 against a concatenation of two
columns in table2. So in pseudocode, it would look something like
this.
fk_table2 FOREIGN KEY (id) REFERENCES table1(id OR
id||'.'||column2) ON DELETE CASCADE;
Do I need a separate constraint for this?
Many thanks for any pointers!
Assuming you actually tried your syntax and received an error...
You cannot have two mutually exclusive constraints since one would always fail.
You need to modify you schema to conform to the definition of a FOREGIN KEY or
maintain integrity via a trigger.
Not enough details to comment on whether what you think you need is indeed a
good design choice.
Database needs are nice in that they can be changed without much argument from
the database. Now, if other developers exhibit these needs then your work
becomes more difficult.
David J.
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