You can have a primary key and a composite index - you can only have one of them as clustered.
Also a foreign key does not need to reference a primary key, it can reference a unique constraint (unique index).
So you can have a composite foreign key ...eg:
if object_id('kev3','U') is not null drop table kev3;
if object_id('kev2','U') is not null drop table kev2;
if object_id('kev','U') is not null drop table kev;
create table kev (
id int not null,
partid1 int not null,
partid2 int not null,
)
alter table kev add constraint PK_kev primary key (id)
create unique index IX_kev_composite on kev(partid1, partid2)
create table kev2 (
id int not null foreign key references kev(id),
blah varchar(100)
)
create table kev3 (
id int not null,
part1 int not null,
part2 int not null,
blah varchar(100)
)
alter table kev3
add constraint FK_kev3 foreign key (part1, part2)
references kev (partid1, partid2)
In this example table kev has both a primary key and a unique composite constraint.
kev2 has a foreign key reference to the PK, and kev3 has a composite foreign key reference to the unique constraint
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