Question

我读到了IS OF TYPE，我希望它应该返回TRUE，FALSE或NULL。

我有两种对象类型：

CREATE TYPE o1 AS OBJECT ( id NUMBER );
/
CREATE TYPE o2 AS OBJECT ( id NUMBER );
/

当我运行下面的代码时，一切正常。

DECLARE
  type1 o1;
BEGIN
   type1 := o1(id=>1); 

   if (type1 IS OF (o1)) then
       DBMS_OUTPUT.PUT_LINE('type1 is o1');                    
   END if;  
END;
/

但是当我尝试跑步时：

DECLARE
  type1 o1;
BEGIN
   type1 := o1(id=>1); 

   if (type1 IS OF (o2)) then
       DBMS_OUTPUT.PUT_LINE('type1 is o1');                    
   END if;  
END;
/

我收到以下例外

Error report:
ORA-06550: line 6, column 21:
PLS-00382: expression is of wrong type
ORA-06550: line 6, column 4:
PL/SQL: Statement ignored
06550. 00000 -  "line %s, column %s:\n%s"
*Cause:    Usually a PL/SQL compilation error.
*Action:

在文档中没有明确的解释，如果某些内容错误，我是否应该捕获异常？或者，我应该在IF条件下假设错误吗？

Answer 1

如果您已将变量声明为O1类型，则可以使用is of [type]条件仅测试您的变量是o1类型还是o1的亚型。这是一个例子（变量必须实例化）：

 -- base type  
 SQL> create or replace type o1 as object(
  2    prop number
  3  )not final;
  4  /

Type created

-- O1's subtype
SQL> create or replace type o2 under o1(
  2    prop1 number
  3  );
  4  /

-- test if the  l_o1 is of O1 type
SQL> declare
  2    l_o1  o1;
  3  begin
  4    l_o1 := o1(prop=>1);
  5    if l_o1 is of (o1)
  6    then
  7      dbms_output.put_line('Yes');
  8    else
  9      dbms_output.put_line('No');
 10    end if;
 11  end;
 12  /

Yes

PL/SQL procedure successfully completed

-- test if the  l_o1 is of O2 type
SQL> declare
  2    l_o1  o1;
  3  begin
  4    l_o1 := o1(prop=>1);
  5    if l_o1 is of (o2)
  6    then
  7      dbms_output.put_line('Yes');
  8    else
  9      dbms_output.put_line('No');
 10    end if;
 11  end;
 12  /

No

PL/SQL procedure successfully completed


-- test if the  l_o2 is of O2 type

SQL> declare
  2    l_o2  o2;
  3  begin
  4    l_o2 := o2(prop=>1, prop1 => 1);
  5    if l_o2 is of (o2)
  6    then
  7      dbms_output.put_line('Yes');
  8    else
  9      dbms_output.put_line('No');
 10    end if;
 11  end;
 12  /

Yes

PL/SQL procedure successfully completed

<强>更新：

Take a look at this获取有关is of[type]的更多信息。通常，变量的数据类型在编译时是已知的，但如果您必须处理动态类型，则可以查看anydata（对象数据类型）。这是一个简单的例子：

 SQL> declare
  2    l_o1 o1;
  3  
  4    -- Here is a procedure(for the sake of simplicity has not
  5    -- been written as a schema object)
  6    -- that doesn't not know
  7    -- variable of what dada type will be passed in
  8    -- at compile time;
  9    procedure DoSomething(p_var anydata)
 10    is
 11    begin
 12      case p_var.gettypename
 13        when 'HR.O1'
 14        then dbms_output.put_line('O1 data type. Do something');
 15        when 'HR.O2'
 16        then dbms_output.put_line('O2 data type. Do something');
 17      else
 18        dbms_output.put_line('Unknown data type');
 19      end case;
 20    end;
 21  
 22  begin
 23    l_o1 := o1(prop =>  1);
 24    DoSomething(anydata.ConvertObject(l_o1));
 25  end;
 26  /

O1 data type. Do something

PL/SQL procedure successfully completed

IS OF TYPE生成异常

1 个答案: