1158. Market Analysis I.sql

SELECTu.user_id,u.join_date,COALESCE(b.orders_in_2019,0)
FROM users_1158 u
LEFT JOIN
 (SELECT buyer_id,COUNT(order_id) AS orders_in_2019
FROM orders_1158
WHERE EXTRACT(YEAR FROM order_date) =2019
GROUP BY buyer_id) b
ONu.user_id=b.buyer_id;