如果您的目标是消除脚本中的错误消息，则可以尝试

begin
   execute immediate 'drop procedure xyz';
exception when others then
   if sqlcode != -4043 then
      raise;
   end if;
end;
/

您还可以在以下之前检查字典视图：

SELECT * FROM USER_PROCEDURES WHERE PROCEDURE_NAME = 'XYZ'

我的解决方案：

DECLARE
  V_NUM NUMBER;
BEGIN     
  SELECT COUNT(*)
  INTO   V_NUM
  FROM   USER_OBJECTS
  WHERE  OBJECT_NAME = 'XYZ'
  AND    OBJECT_TYPE = 'PROCEDURE'; 

  IF V_NUM > 0 THEN
    EXECUTE IMMEDIATE 'DROP PROCEDURE XYZ';
    DBMS_OUTPUT.PUT_LINE('Dropped');
  END IF;

END;
/

完整示例：

declare
   c int;
begin
       select count(*) into c from user_procedures where object_type = 'FUNCTION' and object_name = 'ABC';
       if c = 1 then
          execute immediate 'DROP FUNCTION ABC';
       end if;
end;