FK between rational and xml, between xml and xml

Good day,

I propose to use XPath in DDL to create foreign keys
[1] from rational to xml

create table a(
  a1 num,
  a2 string
);
create table b(
  b1 num,
  b2 num references a(@a2/k/m/n/@n1)
);

[2] from xml to rational

create table a (
  a1 num,
  a2 num
);
create table b (
  b1 num,
  b2 string
);
alter table b add foreign key (@b2/k/m/n/@n1) references a(a2);

[3] from xml to xml

create table a (
  a1 num,
  a2 string
);
create table b (
  b1 num,
  b2 string
);
alter table b add foreign key (@b2/k/m/n/@n1) references a(@a2/p/q/r/@r1);



Dmitry Turin
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