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나에게 꽤나 어려웠던 문제.. https://www.hackerrank.com/challenges/the-report/problem The Report | HackerRank Write a query to generate a report containing three columns: Name, Grade and Mark. www.hackerrank.com Ketty gives Eve a task to generate a report containing three columns: Name, Grade and Mark. Ketty doesn't want the NAMES of those students who received a grade lower than 8. The report must be in de..

Inner Join(동일 조인) Inner Join은 교집합 이라고 할 수 있다. table_A ID name c001 amy c002 yuna table_B ID emp_no from_date c001 1010 2000-01-01 d001 1011 2010-01-05 SELECT a.id, a.name, b.emp_no, b.from_date FROM table_A as a INNER JOIN table_B as b ON a.id = b.id; Inner Join 결과 ID name emp_no from_date c001 amy 1010 2000-01-01 table_A와 table_B에 id가 같은 data만 join되어 출력된다 ! (교집합) table_A와 table_B에 조인컬럼에 해당하는 값이..