has_many_test.sql

CREATE TABLE employees (
  id serial primary key, -- ID
  name text,             -- 名前
  join_year integer,     -- 入社年
  department_id integer  -- 所属部署ID
);

CREATE TABLE departments (
  id serial primary key, -- ID
  name text              -- 部署名
);

INSERT INTO departments (name)
SELECT format('営業%s課', i) FROM generate_series(1, 500) i;

INSERT INTO departments (name)
SELECT format('開発%s課', i) FROM generate_series(1, 500) i;

INSERT INTO employees (name, join_year, department_id)
SELECT format('社員%s', i), 2000 + (random() * 20)::integer, i % 1000 + 1 FROM generate_series(1, 50000) i;