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https://leetcode.com/problems/customers-who-never-order/

 

Customers Who Never Order - LeetCode

Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview.

leetcode.com

[problem]

Write an SQL query to report all customers who never order anything.

Return the result table in any order.

 

[analysis]

1. 두 테이블 left join

2. cutomnerID가 null인 경우 where을 사용해서 리스트 출력해야함

join 과 where은 같이 사용할 수 있따!!

 

[soultion]

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https://www.hackerrank.com/challenges/japan-population/problem

 

Japan Population | HackerRank

Query to the sum of the populations of all Japanese cities in CITY.

www.hackerrank.com

[problem]

[analysis]

population 기준으로 sum 하고 countycode 조건 1개가 존재함

 

[solution]

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