pl sql练习（3）

　　1.s树形结构查询表中的数据：比如emp表中每个员工都有自己的头，即公司中的职位是按层次划分的，类似一个树，因此有时需要按层次显示查询的结果。

　　

 select empno,mgr,ename,job from emp
           start with empno = 7839
           connect by prior empno = mgr;

         EMPNO        MGR ENAME      JOB
     ---------- ---------- ---------- ---------
          7839            KING       PRESIDENT
          7566       7839 JONES      MANAGER
          7788       7566 SCOTT      ANALYST
          7876       7788 ADAMS      CLERK
          7902       7566 FORD       ANALYST
          7369       7902 SMITH      CLERK
          7698       7839 BLAKE      MANAGER
          7499       7698 ALLEN      SALESMAN
          7521       7698 WARD       SALESMAN
          7654       7698 MARTIN     SALESMAN
          7844       7698 TURNER     SALESMAN

         EMPNO        MGR ENAME      JOB
     ---------- ---------- ---------- ---------
          7900       7698 JAMES      CLERK
          7782       7839 CLARK      MANAGER
          7934       7782 MILLER     CLERK

     14 rows selected.

　　2.使用level显示数据所在的层并格式化数据。

 select level,
           lpad(' ',2 * level - 1) || ename as "Ename",
           job
           from emp
           start with ename = 'KING'
           connect by prior empno = mgr;

         LEVEL Ename                          JOB
     ---------- ------------------------------ ---------
             1  KING                          PRESIDENT
             2    JONES                       MANAGER
             3      SCOTT                     ANALYST
             4        ADAMS                   CLERK
             3      FORD                      ANALYST
             4        SMITH                   CLERK
             2    BLAKE                       MANAGER
             3      ALLEN                     SALESMAN
             3      WARD                      SALESMAN
             3      MARTIN                    SALESMAN
             3      TURNER                    SALESMAN

         LEVEL Ename                          JOB
     ---------- ------------------------------ ---------
             3      JAMES                     CLERK
             2    CLARK                       MANAGER
             3      MILLER                    CLERK

     14 rows selected.

　　3.写一个存储过程，向表中随机插入1000条记录
SerialNo：使用序列方式，自增长。
Filepath：使用随机插入6个字母
Partid： 使用随机4位数字
StaffNo：从YTCZ060001……. YTCZ060020 中随机抽取
RecordTime：从2011年8月1日之前的6个月中随机抽取。

 create or replace procedure p_random_corder
 is
   MAXCORDERS constant int :=1000;
   i int :=2;
   day varchar2(100);
   random int;
 begin

   for i in 2..MAXCORDERS loop
     random :=trunc(dbms_random.value(2,8));
     day :=''||
       when  random=7 then ''||lpad(floor(abs(trunc(dbms_random.value(1,31)))),2,'')
      end);
     insert into recordfile values(''||seq_class.nextval,
     upper(chr(trunc(dbms_random.value(97,122))))||
     upper(chr(trunc(dbms_random.value(97,122))))||
     upper(chr(trunc(dbms_random.value(97,122))))||
     upper(chr(trunc(dbms_random.value(97,122))))||
     upper(chr(trunc(dbms_random.value(97,122))))||
     upper(chr(trunc(dbms_random.value(97,122)))),
     trunc(dbms_random.value(1000,9999)),
     'YTCZ0'||trunc(dbms_random.value(60001,60020)),
     to_date(day,'yyyymmdd'));
   end loop;
   dbms_output.put_line('sucess');
   commit;
 end;

　　4.写一个存储过程，删除3个月前的数据

 create or replace procedure p_delete_threedata
  is
  begin
      delete from recordfile where  RecordTime = trunc(add_months(sysdate,-3));
      commit;

  exception
      when others then
      rollback;
  end ;
 /

　　5.写一个job，每隔30天凌晨2点整，系统执行“删除3个月前数据”的存储过程。

 DECLARE
         JobNum NUMBER(5) := 0;
         JobID  NUMBER(5);
 BEGIN
   SELECT COUNT(*) INTO JobNum FROM DBA_JOBS WHERE UPPER(SUBSTRB(WHAT,1,30)) = UPPER('p_delete_threedata');
   IF JobNum > 0 THEN
     SELECT NVL(JOB,0) INTO JobID FROM DBA_JOBS WHERE UPPER(SUBSTRB(WHAT,1,30)) = UPPER('p_delete_threedata');
     IF JobID > 0 THEN
       DBMS_JOB.REMOVE(JobID);
     END IF;
   END IF;
   DBMS_JOB.SUBMIT(JobID, 'p_delete_threedata;', trunc(sysdate,'DD')+1+2/24, 'sysdate+30');
   COMMIT;
 END;
 /

　　6.创建一个触发器tri_emp_sal，要求当向员工表emp中插入记录时，同时更新部门工资统计表（dept_sal）中相应字段的值：如果插入的工资低于1500，则低收入人数(lownum)加1；如果插入的工资高于3000，则高收入人数(highnum)加1。

 先执行下列语句创建dept_sal表并向表中插入实验数据：
 CREATE TABLE dept_sal
 (deptno number(2),
 lownum  number(4),
 highnum number(4));
 insert into dept_sal
 values(10,1,1);
 insert into dept_sal
 values(20,1,3);
 insert into dept_sal
 values(30,1,1);

 CREATE OR REPLACE TRIGGER tri_emp_sal
  AFTER  INSERT  ON EMP
  FOR  EACH  ROW
  BEGIN
  IF :NEW.SAL<1500
  THEN
  UPDATE DEPT_SAL
  SET LOWNUM=LOWNUM+1
  WHERE deptno=:NEW.deptno;
  ELSIF :NEW.SAL>3000
  THEN
  UPDATE DEPT_SAL
  SET HIGHNUM=HIGHNUM+1
  WHERE deptno=:NEW.deptno;
  END IF;
  END;
 /

 测试代码:
 INSERT INTO EMP VALUES(7841,'JOHN','CLERK',7698,'12-dec-87',1000,0,20);
 INSERT INTO EMP VALUES(7912,'LILEI','ANALYST',7839,'05-apr-82',3500,0,10);

　　7.变量作用域

 declare
 v_num number(5,2):=1.23;
     begin
       declare v_num char(10);
       begin
          v_num:=12345;
          dbms_output.put_line(v_num);
       end;
     dbms_output.put_line(v_num);
    end;
    /

 首先会输出12345
 然后输出1.23