pl sql练习（2）

　　1.尽可能了解oracle的功能，因为很多业务逻辑oracle已经为我们做了，比如oracle已经预定义了大量的异常代码，我们不必要写自己的异常而增加代码的复杂度。

例如oracle定义了当找不到符合要求的数据时定义的异常：no_data_found，而很多开发人员经常使用自己的逻辑去判断是否找到数据。

declare
  ln_deptno number;
  ln_tempno number:=1;
begin
  select deptno into ln_deptno
  from scott.dept
  where deptno=ln_tempno;
  dbms_output.put_line(ln_deptno);
exception
  when no_data_found then
  dbms_output.put_line('No deptno for: '||ln_tempno);
end;
/


SQL> @a.sql;
No deptno for: 1

PL/SQL procedure successfully completed.

 　　2.管线表函数,可以把她的返回值作为像数据库表 一样在查询语句中使用。

create or replace type color_hex_code as object
(
  color_name varchar2(10),
  color_code varchar2(10)
);
/
create or replace type color_type as table of color_hex_code;
/
create or replace function f_pipeline_test return color_type pipelined as
begin
  pipe row(color_hex_code('black','#000000'));
  pipe row(color_hex_code('red','#ff0000'));
  pipe row(color_hex_code('green','#00ff00'));
  pipe row(color_hex_code('blue','#0000ff'));
  pipe row(color_hex_code('white','#ffffff'));
  return;
end;
/


SQL> select * from table(f_pipeline_test);

COLOR_NAME COLOR_CODE
---------- ----------
black      #000000
red        #ff0000
green      #00ff00
blue       #0000ff
white      #ffffff

 　　3.传址函数的几种类型

create or replace function adding
  (a in number,b in out number)
  return number is
begin
  b :=b+1;
  return a+b;
end;
/
variable one number;
/
variable two number;
/
begin
  :one :=1;
  :two :=0;
end;
/
variable output number;
/
call adding(:one,:two) into :output;
/
call adding(:one,:two) into :output;
/



select :one, :two from dual;

      :ONE       :TWO
---------- ----------
         1          4

 　　4.使用rollup对分组数据进行汇总

select deptno,sum(sal) from emp where deptno is not null
group by rollup(deptno);

    DEPTNO   SUM(SAL)
---------- ----------
        10       8750
        20      10875
        30       9400
                29025

 　　5.使用cube对分组内每一组的数据和总数据同时汇总，同时包含对不同分组依据进行汇总

select deptno,job,sum(sal) from emp where deptno is not null
group by cube(deptno,job)
order by deptno,job；


   DEPTNO JOB         SUM(SAL)
---------- --------- ----------
        10 CLERK           1300
        10 MANAGER         2450
        10 PRESIDENT       5000
        10                 8750
        20 ANALYST         6000
        20 CLERK           1900
        20 MANAGER         2975
        20                10875
        30 CLERK            950
        30 MANAGER         2850
        30 SALESMAN        5600
        30                 9400
           ANALYST         6000
           CLERK           4150
           MANAGER         8275
           PRESIDENT       5000
           SALESMAN        5600
                          29025

18 rows selected.

 　　6.使用grouping sets 只显示汇总，不列出原始分组数据

SELECT deptno,job,SUM(sal)
        FROM emp
        WHERE deptno IS NOT NULL
        GROUP BY GROUPING SETS(deptno,job)
        ORDER BY deptno,job;

    DEPTNO JOB         SUM(SAL)
    ---------- --------- ----------
           10                 8750
           20                10875
           30                 9400
              ANALYST         6000
              CLERK           4150
              MANAGER         8275
              PRESIDENT       5000
              SALESMAN        5600

　　7.grouping_id函数可以用来标记汇总数据的行，比如第一个维度的汇总用1表示，第二个维度的汇总用2表示，两个维度的所以汇总用3表示。因此可以过滤未汇总的行。

ELECT deptno,job,                                                
          GROUPING_ID(deptno,job),SUM(sal)
          FROM emp
         WHERE deptno IS NOT NULL
         GROUP BY CUBE(deptno,job)
         HAVING GROUPING_ID(deptno,job) > 0
         ORDER BY deptno,job;
 

    DEPTNO JOB       GROUPING_ID(DEPTNO,JOB)   SUM(SAL)
    ---------- --------- ----------------------- ----------
           10                                 1       8750
           20                                 1      10875
           30                                 1       9400
              ANALYST                         2       6000
              CLERK                           2       4150
              MANAGER                         2       8275
              PRESIDENT                       2       5000
              SALESMAN                        2       5600
                                          3      29025

 　　8.利用子查询克隆表结构

CREATE TABLE emp2
               AS
               SELECT *                        
               FROM scott.emp
               WHERE 1=2;
 
           

SQL> SELECT * FROM emp2;
 
           no rows selected   
 

 　　9.用户查看自身表的使用情况(user_extents)

 SELECT segment_name,segment_type,
              tablespace_name,
              bytes/1024/1024 "size",
              blocks from user_extents;        


SEGMENT_NAME         SEGMENT_TYPE       TABLESPACE_NAME                      size     BLOCKS
       -------------------- ------------------ ------------------------------ ---------- ----------
       ORDERS               TABLE              USERS                               .0625          8
       EMP                  TABLE              USERS                               .0625          8
       EMP2                 TABLE              USERS                               .0625          8  
 

　　10.用户查看自身表的使用情况(user_segments)

SELECT segment_name,segment_type,tablespace_name,
             bytes/1024/1024 byt,buffer_pool
             FROM user_segments;

  SEGMENT_NAME                             SEGMENT_TYPE       TABLESPACE_NAME             BYT BUFFER_
       ---------------------------------------- ------------------ ------------------- ---------- -------
       EMP2                                     TABLE              USERS                    .0625 DEFAULT
       EMP                                      TABLE              USERS                    .0625 DEFAULT
       ORDERS                                   TABLE              USERS                    .0625 DEFAULT
       BIN$iZfhhmba19rgQKjAZQETvA==$0           TABLE              USERS                    .0625 DEFAULT
       BIN$iZfhhmbZ19rgQKjAZQETvA==$0           TABLE              USERS                    .0625 DEFAULT
       BIN$iZfhhmbY19rgQKjAZQETvA==$0           TABLE              USERS                    .0625 DEFAULT