oracle的聚集合函式

//聚集合函式
max,min,avg,count,sum

select count(*) from dept;
select count(deptno) from dept;

//user,decode,nvl
select user from dual;
select sum(decode(a1,'abc',1,0)),sum(decode(a1,'bca',1,0)) from aa;
select a1,nvl(a2,'NULL') from aa;
select * from aa where a2 is null;
select * from aa where a2 is not null;
select * from aa order by a1 asc;
select * from aa order by a1 asc;
//查詢不重複的
select distinct a1 from aa;

分組查詢
select id,sum(price) from aa group by id;