Plsql 在if条件pl/sql中如何处理异常

当我在plsql中编写if-else条件以使用if-conditopn检查它是偶数还是奇数时，我需要您的帮助。若我输入字符，那个么它将引发一个错误。如何使用异常来处理它以理解客户端。帮帮我

declare
num number:=&number;
begin
if num=1 then
dbms_output.put_line('composite');
else if mod(num,2)=0 then
dbms_output.put_line('even');
else if mod(num,2)=1 then
dbms_output.put_line('odd');
else
dbms_output.put_line('enter proper data');
end if;
end if;
end if;
end;
/

---

请参见以下工作示例：

declare
  -- user input is always a string so treat it as a string
  v_input varchar2(32767) := '&number';
  num number;
begin
  -- convert input to a number. to_number() throws if input string can't be
  -- converted to a number. see to_number() documentation for details.
  -- the conversion has to happen inside begin-end block because the exception
  -- handler of the block won't catch exceptions raised in declare block.
  num:=to_number(v_input);

  -- do your math
  if num=1 then
    dbms_output.put_line('composite');
  elsif mod(num,2)=0 then
    dbms_output.put_line('even');
  elsif mod(num,2)=1 then
    dbms_output.put_line('odd');
  else
    dbms_output.put_line('enter proper data');
  end if;
exception
  -- the exception raised by to_number()
  when value_error then
    dbms_output.put_line('not a valid number: ' || v_input);
  -- all other exceptions are still raised to the caller.
end;
/

示例结果：

SQL> @so
Enter value for number: 1
old   2:   v_input varchar2(32767) := '&number';
new   2:   v_input varchar2(32767) := '1';
composite

PL/SQL procedure successfully completed.

SQL> @so
Enter value for number: 2
old   2:   v_input varchar2(32767) := '&number';
new   2:   v_input varchar2(32767) := '2';
even

PL/SQL procedure successfully completed.

SQL> @so
Enter value for number: 3
old   2:   v_input varchar2(32767) := '&number';
new   2:   v_input varchar2(32767) := '3';
odd

PL/SQL procedure successfully completed.

SQL> @so
Enter value for number: foo
old   2:   v_input varchar2(32767) := '&number';
new   2:   v_input varchar2(32767) := 'foo';
not a valid number: foo

PL/SQL procedure successfully completed.

SQL> 

---

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