【PL/SQL】异常处理：

如果在PLSQL块中没有做异常处理，在执行PLSQL块时，出现异常，会传递到调用环境，导致程序运行出错！

SCOTT@ prod> declare
   2
   3   v_ename emp.ename%type;
   4   v_sal   emp.sal%type;
   5
   6  begin
   7
   8    select ename,sal into v_ename,v_sal from emp where deptno=&n;
   9
  10    dbms_output.put_line(v_ename||':'||v_sal);
  11
  12
  13  end;

1.预定义异常：
TOO_MANY_ROWS  在隐式游标处理时，select 返回行数超过一行

SQL> declare
  2
  3   v_ename emp.ename%type;
  4   v_sal   emp.sal%type;
  5
  6  begin
  7
  8    select ename,sal into v_ename,v_sal from emp where deptno=&n;
  9
 10    dbms_output.put_line(v_ename||':'||v_sal);
 11
 12  exception
 13    when too_many_rows then
 14         dbms_output.put_line('You return rows more than one !');
 15    when others  then
 16         dbms_output.put_line('Other''s error !');
 17  end;

2.NO_DATA_FOUND   在访问数据时，没有发现数据。

SQL> declare
  2
  3   v_ename emp.ename%type;
  4   v_sal   emp.sal%type;
  5
  6  begin
  7
  8    select ename,sal into v_ename,v_sal from emp where empno=#
  9
 10    dbms_output.put_line(v_ename||':'||v_sal);
 11
 12  exception
 13    when no_data_found then
 14         dbms_output.put_line('No data found ,Please input correct number !');
 15    when others  then
 16         dbms_output.put_line('Other''s error !');
 17  end;

3.ZERO_DIVIDE   除数为零

SQL> declare
  2
  3    v_num1 number :=10;
  4    v_num2 number ;
  5    v_num3 number;
  6
  7  begin
  8     v_num2 := &nn;
  9
 10     v_num3 := v_num1 / v_num2 ;
 11
 12     dbms_output.put_line( 'Number is : '||v_num3);
 13  exception
 14      when zero_divide then
 15       dbms_output.put_line( 'Divisor is equal to zero,Please input correct Number !');
 16      when others  then
 17      dbms_output.put_line('Other''s error !');
 18  end;