oracle——笔记——连接查询

亦凉 2023-10-02 08:14 6阅读 0赞

create table emp2 ( empno number(4),
                        ename varchar2(10),
                        job varchar2(9),
                        mgr number(4),
                        hiredate date,
                        sal number(7,2),
                        comm number(7,2),
                        deptno number(2) 
                     );
    -----------------------------------------------------------------------------------------------------------
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7369, 'SMITH', 'CLERK', 7902, to_date('17-12-1980', 'dd-mm-yyyy'), 800.00, null, 20);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7499, 'ALLEN', 'SALESMAN', 7698, to_date('20-02-1981', 'dd-mm-yyyy'), 1600.00, 300.00, 30);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7521, 'WARD', 'SALESMAN', 7698, to_date('22-02-1981', 'dd-mm-yyyy'), 1250.00, 500.00, 30);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7566, 'JONES', 'MANAGER', 7839, to_date('02-04-1981', 'dd-mm-yyyy'), 2975.00, null, 20);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7654, 'MARTIN', 'SALESMAN', 7698, to_date('28-09-1981', 'dd-mm-yyyy'), 1250.00, 1400.00, 30);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7698, 'BLAKE', 'MANAGER', 7839, to_date('01-05-1981', 'dd-mm-yyyy'), 2850.00, null, 30);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7782, 'CLARK', 'MANAGER', 7839, to_date('09-06-1981', 'dd-mm-yyyy'), 2450.00, null, 10);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7788, 'SCOTT', 'ANALYST', 7566, to_date('19-04-1987', 'dd-mm-yyyy'), 3000.00, null, 20);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7839, 'KING', 'PRESIDENT', null, to_date('17-11-1981', 'dd-mm-yyyy'), 5000.00, null, 10);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7844, 'TURNER', 'SALESMAN', 7698, to_date('08-09-1981', 'dd-mm-yyyy'), 1500.00, 0.00, 30);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7876, 'ADAMS', 'CLERK', 7788, to_date('23-05-1987', 'dd-mm-yyyy'), 1100.00, null, 20);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7900, 'JAMES', 'CLERK', 7698, to_date('03-12-1981', 'dd-mm-yyyy'), 950.00, null, 30);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7902, 'FORD', 'ANALYST', 7566, to_date('03-12-1981', 'dd-mm-yyyy'), 3000.00, null, 20);
    
    insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
    values (7934, 'MILLER', 'CLERK', 7782, to_date('23-01-1982', 'dd-mm-yyyy'), 1300.00, null, 10);
    
    =============================================================================================================================
    
    create table dept2 ( deptno number(2),
                         dname varchar2(14),
                         loc varchar2(13)
                       );
    
    ----------------------------------------------------
    
    insert into dept2 (DEPTNO, DNAME, LOC)
    values (10, 'ACCOUNTING', 'NEW YORK');
    
    insert into dept2 (DEPTNO, DNAME, LOC)
    values (20, 'RESEARCH', 'DALLAS');
    
    insert into dept2 (DEPTNO, DNAME, LOC)
    values (30, 'SALES', 'CHICAGO');
    
    insert into dept2 (DEPTNO, DNAME, LOC)
    values (40, 'OPERATIONS', 'BOSTON');
    
    ============================================================
    
    create table salgrade2 ( grade number,
                             losal number,
                             hisal number
                           );
    
    --------------------------------------------------
    
    insert into salgrade2 (GRADE, LOSAL, HISAL)
    values (1, 700, 1200);
    
    insert into salgrade2 (GRADE, LOSAL, HISAL)
    values (2, 1201, 1400);
    
    insert into salgrade2 (GRADE, LOSAL, HISAL)
    values (3, 1401, 2000);
    
    insert into salgrade2 (GRADE, LOSAL, HISAL)
    values (4, 2001, 3000);
    
    insert into salgrade2 (GRADE, LOSAL, HISAL)
    values (5, 3001, 9999);
    
    
    ========================================================
    
    select * from emp2;
    
    select * from dept2;
    
    select * from salgrade2;
    
    =====================================
    select * from emp2;        --employee2 员工表
    select * from dept2;       --department2 部门表
    select * from salgrade2;   -- salary grade2 工资等级表
    
    -----------------------------------------------------
    emp2
    
    empno    员工编号
    ename    员工姓名
    job      工作/工种
    mgr      manager上级编号
    hiredate 入职日期
    sal      salary 工资
    comm     奖金/津贴
    deptno   部门编号
    ---------------------
    
    dept2
    
    deptno  部门号
    dname   部门名称
    loc     所在地
    ---------------------------
    salgrade2
    
    grade                   等级
    losal lowest salary     最低工资
    hisal high salary       最高工资
    
    =============================================
    
    ================================================================================================
    
    
    多表联合查询/多表连接
    
     内连接(等值连接、不等值连接)
     外连接(左外、右外、全外)
     自连接
     
    等值连接
    
    查询员工姓名和员工所在部门的部门名称:
    
    select *
    from emp2,dept2
    where emp2.deptno = dept2.deptno; ---连接条件
    
    select ename,dname
    from emp2,dept2
    where emp2.deptno = dept2.deptno;
       
    
    查询员工编号、入职日期、部门名称
    
    select emp.empno,emp.hiredate,dept.dname
    from emp2,dept2
    where emp2.deptno = dept2.deptno;
       
    
    select e.empno,e.hiredate,d.dname
    from emp2 e,dept2 d
    where e.deptno = d.deptno;
    
    
    
    
    
    
    
    查询 SALES 部门(SALES 是部门名称) 的员工信息:
    
    select e.*
    from emp2 e,dept2 d
    where e.deptno = d.deptno and d.dname = 'SALES';
        
    
    
    
    
     
    查询工作类别是ANALYST 的员工的工资、部门号和部门所在地:
    
    select e.sal,d.deptno,d.loc
    from emp2 e,dept2 d
    where e.deptno = d.deptno and e.job = 'ANALYST';
     
    
    
    
    
    
    
    
    
    
    不等值连接
     
    查询每个员工的工资等级:
     
    select * from emp2;
    
    select * from salgrade2;
     
    select *
    from emp2 e,salgrade2 s
    where e.sal between s.losal and s.hisal;
    
     
    
    
    
    
    
    
    
    ----------------------------------------------------------------------------
    
    
    
    
    
    
    
    
    外连接：
    
    
    作用：查询不满足连接条件的数据
    
    等值查询：两边的表如果都有数值相等，且配对的才会显示出来；
    
     select * from emp2 e,dept2 d
     where e.deptno = d.deptno;
     
     
    
    
    
    
    
    
    右外：  右边的表在左边中如果匹配不到数据，也会显示出来。
     
     select * from dept2;
     
     select * from emp2 e,dept2 d
     where e.deptno(+) = d.deptno;
     
    
    
    
    
    
    
    左外： 左边表中的数据如果在右边表中匹配不到数据，也会显示出来；
     
     select * from emp2;
    
     insert into emp2(empno) values(1122);
     
     select * from emp2 e,dept2 d
     where e.deptno = d.deptno(+); 
     
     delete from emp2 where emp2.empno = 1122;
     
     
     select * from emp2 e,dept2 d
     where e.deptno(+) = d.deptno(+);  ---不存在这种写法 
     
    
    
    
    
    
    
     ---------------------------------------------------------------------------------------
     
    
    
    
    
    
    
    外连接的另外一种写法：
    
    
    左外：
    
    
    select * from emp2;
    
    insert into emp2(empno) values(1122);
     
    delete from emp2 where emp2.empno = 1122;
    
    
    
    
    select * 
    from emp2 e left outer join dept2 d
    on e.deptno = d.deptno;                  left    显示左边表不满足条件的数据
                                             outer   可以省略
                                             on      只能写连接条件，其他条件 写到where里
     
    
                                            
    右外：
                                          
    select * 
    from emp2 e right outer join dept2 d
    on e.deptno = d.deptno;   
    
    
    
    
    
    
    
    
    
    
    全外：如果两个表中都有相互匹配不到的数据，则都会显示出来；
    
    
    select * from emp2;
    
    insert into emp2(empno) values(1122);
     
    delete from emp2 where emp2.empno = 1122;
    
    
    select *    
    from emp2 e full outer join dept2 d
    on e.deptno = d.deptno;    
       
    
    ------------------------------------------------------------------------------------ 
       
    查询出没有员工的部门信息：
    
    select d.* 
    from emp2 e right outer join dept2 d
    on e.deptno = d.deptno
    where e.empno is null; 
    
    
    
    
    
    
    
    
    
    自连接:
    
    查询员工姓名和他的上级姓名:
    
    select * from emp2;
     
    员工的mgr = 上级的empno
     
    select *
    from emp2 worker,emp2 manager
    where worker.mgr = manager.empno;
     
     
      select * from emp2 worker;
      select * from emp2 manager;
      
      
    
    
    
    
    
    
    查询出入职比上级早的员工:
    
    select *
    from emp2 worker,emp2 manager
    where worker.mgr = manager.empno and worker.hiredate < manager.hiredate;