data/schema_map.json

{
  "employee": {
    "columns": ["emp_id", "emp_name", "dept_id", "salary"],
    "pk": "emp_id",
    "fks": {"dept_id": "department"}
  },
  "department": {
    "columns": ["dept_id", "dept_name"],
    "pk": "dept_id",
    "fks": {}
  },
  "payroll": {
    "columns": ["payroll_id", "emp_id", "amount", "date"],
    "pk": "payroll_id",
    "fks": {"emp_id": "employee"}
  }
}