database high quiz solution

src/kr/co/swh/lecture/database/quiz_high_solve

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+1) 직원 이름 중 '샘' 이라는 글자가 들어간 직원들의 총 판매금액
+SELECT SUM(c.price) '총합' 
+FROM employees a, sales b, items c 
+WHERE a.employee_id = b.employee_id and b.item_id = c.item_id AND a.name LIKE '%샘%';
+
+2) 제품별 판매횟수를 큰 순서로 정렬
+SELECT b.item_name, COUNT(1) '갯수' FROM sales a, items b 
+WHERE a.item_id = b.item_id 
+GROUP BY a.item_id ORDER BY COUNT(1) desc;
+
+3) 가장 판매 횟수가 높은 제품 이름
+SELECT item_name, count(*) as C FROM sales b, items c WHERE b.item_id = c.item_id
+group by c.item_id
+order by C desc 
+limit 1;
+
+4) 가장 판매금액이 높은 직원 이름
+SELECT a.name, sum(c.price) as S FROM employees a, sales b, items c 
+WHERE a.employee_id = b.employee_id and b.item_id = c.item_id
+group by a.employee_id
+order by S desc 
+limit 1;
+
+5) 각 position별 시급(hourly_pay)이 높은 직원 이름
+SELECT a.name, q.* 
+FROM employees a, (SELECT position, max(hourly_pay) hourly_pay FROM employees GROUP BY POSITION) q 
+WHERE a.position = q.position AND a.hourly_pay = q.hourly_pay;