–1.列出至少有一个员工的所有部门。
select dname from dept where deptno in(select deptno from emp);
–2.列出薪金比“SMITH”多的所有员工。
select * from emp where sal>(select sal from emp where ename =‘SMITH’);
–3.列出所有员工的姓名及其直接上级的姓名。
select a.ename,(select ename from emp b where b.empno=a.mgr) as boss_name from emp a;
–4.列出受雇日期早于其直接上级的所有员工。
select a.ename from emp a where a.hiredate<(select hiredate from emp b where b.empno=a.mgr);
–5.列出部门名称和这些部门的员工信息，同时列出那些没有员工的部门
select a.dname,b.empno,b.ename,b.job,b.mgr,b.hiredate,b.sal,b.deptno
from dept a left join emp b on a.deptno=b.deptno;
–6.列出所有“CLERK”(办事员)的姓名及其部门名称。
select a.ename,b.dname from emp a join dept b on a.deptno=b.deptno and a.job=‘CLERK’;
–7.列出最低薪金大于1500的各种工作。
select distinct job as HighSalJob from emp group by job having min(sal)>1500;
–8.列出在部门“SALES”(销售部)工作的员工的姓名，假定不知道销售部的部门编号。
select ename from emp where deptno=(select deptno from dept where dname=‘SALES’);
–9.列出薪金高于公司平均薪金的所有员工。
select ename from emp where sal>(select avg(sal) from emp);
–10.列出与“SMITH”从事相同工作的所有员工。
select ename from emp where job=(select job from emp where ename=‘SMITH’);
–11.列出薪金等于部门30中员工的薪金的所有员工的姓名和薪金。
select a.ename,a.sal from emp a where a.sal in (select b.sal from emp b where b.deptno=30)
–12.列出薪金高于在部门30工作的所有员工的薪金的员工姓名和薪金。
select ename,sal from emp where sal>(select max(sal) from emp where deptno=30);
–13.列出在每个部门工作的员工数量、平均工资和平均服务期限。
select (select b.dname from dept b where a.deptno=b.deptno) as deptname ,count(deptno) as deptcount,avg(sal) as deptavgsal
from emp a group by deptno;
–14.列出所有员工的姓名、部门名称和工资。
select a.ename,(select b.dname from dept b where b.deptno=a.deptno) as deptname,sal from emp a;
–15.列出所有部门的详细信息和部门人数。
select a.deptno,a.dname,a.loc,(select count(deptno) from emp b where b.deptno=a.deptno group by b.deptno) as deptcount from dept a;
–16.列出各种工作的最低工资。
select job,avg(sal) from emp group by job;
–17.列出各个部门的MANAGER(经理)的最低薪金。
select deptno,min(sal) from emp where job=‘MANAGER’ group by deptno;
–18.列出所有员工的年工资,按年薪从低到高排序。
select ename,(sal+nvl(comm,0))*12 as salpersal from emp order by salpersal;
–19 查询雇员表中，姓名为SMITH的雇员，截止到今天共工作了多少周，则可以使用如下的SQL语句?
select round((sysdate-hiredate)/7) as “Weeks” from emp where ename=‘SMITH’;
–20 查询各部门的最高薪水、最低薪水、平均薪水….?
select deptno,max(sal),min(sal),avg(sal) from emp group by deptno;