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