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**SQL多表连查** |
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--查询员工和部门信息select * from emp e,dept d where e.deptno=d.deptno--查询员工姓名，部门名称select e.ename,d.dname from emp e,dept d where e.deptno = d.deptno--查询所有员工姓名，部门名称select e.*, d.dname from emp e,dept d where e.deptno=d.deptno--查询工资大于3000的员工姓名，工资和部门名称select e.ename,e.sal,d.dname from emp e,dept d where e.deptno=d.deptno and e.sal>=3000 |
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--非等值查询--查询公司工资等级select * from emp e,salgrands where e.sal<=s.hisal and e.sal>s.losalselect * from salagrade |
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--外链接--左外连接select*from emp e,dept d where e.deptno=d.deptno(+)--右外连接select*from emp e,dept d where e.deptno(+)=d.deptno |
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--自连接--查询员工姓名和经理姓名select e1.ename ,e2.ename from emp e1,emp e2 where e1.mgr=e2.deptno--查询员工姓名、经理姓名和其他经理姓名select e1.ename,e2.ename,e3.ename from emp e1,emp e2, emp e3 where e1.mgr=e2.empno and e2.empno=e3.empno |
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**以上为92版仅在面试出现** |
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--SQL99 表连接--交叉连接 cross joinselect *from emp e cross join dept d--自然连接 natural join select *from emp natural join dept--using select e.ename,deptno from emp e join dept d using(deptno)--on 自定义连接select *from emp e join dept d on e.deptno=d.deptnoselect *from emp e1 join emp e2 on e1.mgr=e2.empno--查询员工的姓名、经理及其经理的名字select e1.ename,e2.ename,e3.ename from emp e1 join emp e2 on e1.mgr=e2.empno join emp e3 on e2.mgr=e3.empno--SQL99 inner join 两边都合法的数据select*from emp e inner join dept d on e.deptno=d.deptno--left join 以左表为主select*from emp e left join dept d on e.deptno=d.deptno--right join 以右表为主select*from emp e right join dept d on e.deptno=d.deptno--full join 全连 取两个表的所有数据select*from emp e full join dept d on e.deptno=d.deptno----查询员工的姓名、经理及其经理的名字和部门名字select e1.ename, d.dname, e2.ename, d2.dname from emp e1 left join dept d on e1.deptno = d.deptno left join emp e2 on e2.mgr = e2.empno left join dept d2 on d2.deptno = d2.deptno |
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**子查询** |
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--比CLARK工资高的人select SAL from emp where ename='CLARK'select *from emp where sal>(select SAL from emp where ename='CLARK')--查询工资高于平均工资的雇员姓名和工资select avg(sal) from emp select ename,sal from emp where sal>(select avg(sal) from emp )--查询同SCOTT同部门的且工资比他低的员工的名字和工资select deptno from emp where ename='SCOTT'select sal from emp where ename='SCOTT'select ename, sal from emp where deptno = (select deptno from emp where ename = 'SCOTT') and sal < (select sal from emp where ename = 'SCOTT')--查询和'SMITH','SCOTT','CLARK'同一个部门的员工姓名select distinct deptno from emp where ename in('SMITH','SCOTT','CLARK')select * from emp where deptno in (select distinct deptno from emp where ename in ('SMITH', 'SCOTT', 'CLARK'))--查询和'SMITH', 'SCOTT', 'CLARK'同一个部门并不包含他们三个的员工姓名 and ename not in ('SMITH', 'SCOTT', 'CLARK')--查询工资最高的员工名字和工资select ename,sal from emp where sal=(select max(sal)from emp )--查询职务和'SCOTT'相同但是比'SCOTT'雇佣时间早的雇员信息select * from emp where job = (select job from emp where ename = 'SCOTT') and hiredate < (select hiredate from emp where ename = 'SCOTT')--查询工资比'SCOTT'高或者雇佣时间比'SCOTT'早的雇员编号和姓名select empno,ename from emp where job = (select job from emp where ename = 'SCOTT') and hiredate < (select hiredate from emp where ename = 'SCOTT') |
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**多行子查询** |
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--查询工资低于任何一个“CLERK”的工资的雇员信息select*from emp where sal all (select sal from emp where job = 'SALESMAN')--查询部门20中职务同部门10的雇员一样的雇员信息。select *from emp where job in (select job from emp where deptno=10)and deptno=20--查询在雇员中有哪些人是经理人select * from emp where empno in (select distinct mgr from emp where mgr is not null or mgr != '')--找出部门编号为20的所有员工中收入最高的职员select ename from emp where sal = (select max(sal) from emp where deptno = 20) and deptno = 20</any(select> |