（1）listagg()作用：将数据表某一列的内容转换为一行，并且用符号隔开；
select job,listagg(ename,’,’) within group(order by job) from emp group by job (2)pivot()子句应用：实现行转列： select * from (select job,sal,deptno from emp) pivot(sum(sal) as a for deptno in(10 as d10,20 as d20, 30 as d30)) order by 1
