diff --git a/schema/020_usr.sql b/schema/020_usr.sql
index 64493d4..56390f0 100644
--- a/schema/020_usr.sql
+++ b/schema/020_usr.sql
@@ -33,10 +33,19 @@ create table public.usr
   , uid      uuid                not null default gen_random_uuid()
   , deleted  boolean             not null default false
   , tag      public.usr_tag      not null
+  , discrim  int                 not null
   , password public.hashed_text  not null
   , email    public.email        not null unique
+  , unique (tag, discrim)
   );
 
+create function public.usr_tag_count(tag public.usr_tag) returns int language sql stable as $$
+  select count(*) from public.usr u where u.tag = tag;
+$$;
+
+alter table public.usr
+alter column discrim set default public.usr_tag_count(tag);
+
 insert into public.usr (tag, password, email)
 values (usr_tag_of_string('system'), hashed_text_of_string(''), email_of_string(''));