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If constraints are stored in the DB then:
  advantages
1) if the application programmer forgets or does not know about the
rule the database will still protect the data
2) the db is usually very efficient at checking the constraints,
usually more so than the application
3) PK, UK, and FK defined in the database serve as a form of
documentation about the relationships between the tables

  disadvantages
1) the error message returned to a user is pretty ugly (though the
program can check for and format user friendly error messages)
2) where the rule is to only be selectly enforced you usually need to
do it in the application
3) FK's make table/index maintenance slightly more difficult for the
DBA (You can not drop and rebuild a PK index in another tablespace if
there are 5 FK that reference it without first disabling the FK's, and
then you must remember to re-establish the FK after rebuilding the
index.)

There may be other considerations but these are what comes to mind
right now.

soon i update this post

soon i update this post

soon i update this post