LeetCode题解(1158)：市场分析I(SQL)

题目：原题链接（中等）

标签：SQL

解法	时间复杂度	空间复杂度	执行用时
Ans 1 (Python)			2040ms (5.04%)
Ans 2 (Python)
Ans 3 (Python)

解法一：

SELECT user_id AS buyer_id,
       join_date,
       IFNULL(orders_in_2019, 0) AS orders_in_2019
FROM Users AS U
         LEFT JOIN
     (SELECT buyer_id, COUNT(order_id) AS orders_in_2019
      FROM Orders
      WHERE YEAR(order_date) = 2019
      GROUP BY buyer_id) AS T ON U.user_id = T.buyer_id;