plsql的命令行窗口显示DBMS_OUTPUT的打印结果

      最近想了解下Oracle的Case When怎样用，弄了个简单的例子测试，如下:

     

  DECLARE
    v_num  NUMBER := &sv_num;
    v_flag NUMBER;
  BEGIN
    CASE
      WHEN MOD(v_num, 2) = 0 THEN
        DBMS_OUTPUT.PUT_LINE(v_num || ' is even number');
      ELSE
        DBMS_OUTPUT.PUT_LINE(v_num || ' is odd number');
    END CASE;
  END;

   测试半天发现，结果总是：PL/SQL procedure successfully completed

   我的打印语句呢？原来还要这样设置：

    

set serveroutput on;

    再测试结果正常：

   

-2 is even number
 
PL/SQL procedure successfully completed

    这些简单的知识不用就忘记了，写下备忘。