求优化
帮我优化一下

SQL code

/*1.1*/select * from emp where nvl(comm,0)<500;/*1.2*/select sum(decode(s.grade, 1, 1)) 等级一,       sum(decode(s.grade, 2, 1)) 等级二,       sum(decode(s.grade, 3, 1)) 等级三,       sum(decode(s.grade, 4, 1)) 等级四,       sum(decode(s.grade, 5, 1)) 等级五from emp e, salgrade swhere e.sal >= losal and e.sal <= hisal;/*1.3*/select sal,sum(sal),avg(sal) from emp eselect round(123.345,2) from dualselect e.ename ,       e.sal,       sum(sal) over(partition by deptno) sum_sal,       round(avg(sal) over(partition by deptno),2) avg_sal  from emp e;/*1.4*/select e.ename,       e.deptno,       rank() over(partition by deptno order by sal desc)-1 高于工资人数,       rank() over(partition by deptno order by sal)-1 低于工资人数  from emp e ;/*1.5*/select  ename,deptno,sal,rn "工资排名" from (select deptno,ename,sal,row_number() over(partition by deptno order by sal desc) rnfrom emp) e; select * from emp where ename='KING';/*1.6*/select ename,job,sal,avg_sal "工种平均工资"from(select ename,job,sal,round(avg(sal) over(partition by job),2) avg_sal,empno from emp)where sal<avg_sal order by empno;/*1.7*//*1.8*/select e_before.ename "时间点入职前ENAME",e_before.job "时间点入职前JOB",e_before.sal "时间点入职前SAL",e_after.ename "时间点入职后ENAME",e_after.job "时间点入职后JOB",e_after.sal "时间点入职后SAL"from(select * from emp where to_char(hiredate,'YYYY-MM-DD')<'1981-09-09') e_before,(select * from emp where to_char(hiredate,'YYYY-MM-DD')>'1981-09-09') e_afterwhere e_before.job=e_after.job;/*1.9*/select e.ename,e.job,d.dnamefrom emp e,dept dwhere e.job=(select job from emp where ename='SCOTT') and e.deptno=d.deptno and e.ename!='SCOTT';  /*1.10*/select distinct  e1.deptno,          e1.job,          avg(sal) over(partition by e1.deptno,e1.job) "平均工资"from emp e1,(select e.deptno,e.job from emp e group by e.deptno,e.job having count(*)>=2) e2where e1.deptno=e2.deptno and e1.job=e2.joborder by "平均工资";

[解决办法]
运算太多了 建议做临时表吧
先做insert into select * from .... 操作
然后在做简单的查询操作

[解决办法]
提问不清晰，不知道要怎么优化
[解决办法]
要优化哪句