joins

-- INNER JOIN: Only matching rows
SELECT
  users.name,
  orders.order_number,
  orders.total
FROM users

-- Basic LATERAL join
SELECT
  u.username,
  recent.order_id,
  recent.total,
  recent.created_at

import pandas as pd

customers = pd.read_parquet('customers.parquet')
orders = pd.read_parquet('orders.parquet')

assert customers['customer_id'].is_unique, 'customer table must be unique by customer_id'