基本SQL聚合

Question

我有两个表：runner（r_name（主键），miles，week_id）和WEEKDAYS（did，day_of_week）。 runner.week_id引用Weekdays.did。

如何找到平均里程最长的星期几？

Answer 1

创建一个内部查询，将GROUPS运行程序用于星期几。使用带限制的订单来选择按周数列出的最高入口。然后选择具有该ID的周：

SELECT *
FROM weekdays
WHERE
week_id IN (
  SELECT week_id
  FROM runner
  GROUP BY week_id
  ORDER BY SUM(miles) DESC
  LIMIT 1
)

使用联接：

SELECT *
FROM weekdays
JOIN runner
ON runner.week_id = weekdays.id
GROUP BY runner.week_id
ORDER BY SUM(runner.miles) DESC
LIMIT 1