▣ group by ( sum , min , max , count , avg ) > ORACLE

▣ select * from notice; 

① select writer,sum(hit) from notice group by writer; --writer 별 총 조회수

② select writer,min(hit) from notice group by writer; --writer 별 최저 조회수

③ select writer,max(hit) from notice group by writer; --writer 별 최고 조회수

④ select writer,avg(hit) from notice group by writer; --writer 별 총 조회수 

⑤ select writer,count(*) from notice group by writer; --writer 별 총 작성수

⑥ select writer,count(*) from notice group by writer HAVING count(*) > 3; --group by 절에서 조건은 HAVING 이용