codewars--两张表连接查询的操作

题目：For this challenge you need to create a simple SELECT statement that will return all columns from the people table, and join to the sales table so that you can return the COUNT of all sales and RANK each person by their sale_count.

people table schema

• id
• name

sales table schema

• id
• people_id
• sale
• price

You should return all people fields as well as the sale count as "sale_count" and the rank as "sale_rank".

NOTE: You're solution should use pure SQL. Ruby is used within the test cases to do the actual testing.

解决方案：

SELECT 

  p.*,

  COUNT(s) as sale_count, 

  RANK() OVER (ORDER BY sum(s.price) DESC) as sale_rank

  FROM people p

  JOIN sales s ON s.people_id = p.id

  GROUP BY p.id