EMP（EMPNO，ENAME，JOB，MGR，HIREDATE，SAL，COMM，DEPTNO） DEPT（DEPTNO，DNAME，LOC）（急急急）

1、SELECT e.ename,e.job,e.hiredate,e.sal,e.sal*12 FROM emp e ;
2、SELECT v.deptno,v.dname FROM (SELECT AVG(e.sal) avgsal,d.deptno,
d.dname FROM emp e LEFT JOIN dept d ON e.deptno=d.deptno
GROUP BY e.deptno,d.deptno,d.dname)v
WHERE v.avgsal>2000;
3、SELECT e.* FROM emp e LEFT JOIN dept d ON e.deptno=d.deptno
WHERE d.dname='SALES'
AND e.sal >(SELECT DISTINCT AVG(e.sal) OVER (PARTITION BY e.deptno) FROM emp e LEFT JOIN dept d ON e.deptno=d.deptno
WHERE d.dname='RESEARCH');
4、create bitmap index mgr_bit on emp(mgr);
5、SELECT * FROM emp
WHERE (sal,deptno) IN (SELECT MAX(e.sal),e.deptno
FROM emp e GROUP BY e.deptno);