CREATE TABLE a (
  id   BIGSERIAL PRIMARY KEY,
  a TEXT NOT NULL
);

CREATE TABLE b (
  id BIGSERIAL PRIMARY KEY,
  b TEXT NOT NULL,
  a_id BIGINT NOT NULL REFERENCES a (id)
);

CREATE TABLE c (
  id BIGSERIAL PRIMARY KEY,
  c TEXT NOT NULL,
  a_id BIGINT NOT NULL REFERENCES a (id)
);

CREATE TABLE d (
  id BIGSERIAL PRIMARY KEY,
  d TEXT NOT NULL,
  a_id BIGINT NOT NULL REFERENCES a (id)
);

CREATE TABLE e (
  id BIGSERIAL PRIMARY KEY,
  e TEXT NOT NULL,
  a_id BIGINT NOT NULL REFERENCES a (id)
);