Re: How to do unique users

Around 03:09 on Feb 9, 2003, gearond@cvc.net said:

# I have the following tables (mucho simplified):
#
# usrs{
# serial usr_id,
# var(54) username);
#
# addrs(
# serial addr_id,
# var(54) addr};
#
# usr_addr_type(
# serial usr_addr_type_id,
# var(16) type -- one of which is 'primary'};
#
# usr_addrs{
# int4 usr_id, --FK to usrs table
# int4 addr_id, -- FK to addrs table
# int4 usr_addr_type_id -- FK to usr_addr_type table);
#
# ================================
# My problem: The usrs can have as many addresses as there are types. The
# addresses are also used for 'org_addrs' in combination with 'org_addr_types'.
# (This explains the 'usr_addrs' table)
#
# I want to EFFECTIVELY do a unique index on:
#
# 'usrs.username' their 'primary' address in usr_addrs'. How would I have many
# addresses in 'usr_addrs' for a particular address, but one of them used for
# uniqueness of the of the 'usr'
# ?

    The easiest way is to have a primary address ID on the user table
then have a mapping for alternate addresses.

    Otherwise, you can do what you're asking with a trigger.

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