我想写一个查询，对于我的日期参数'P_D_IN_END_DT'，如果传递了'01/01/1900'或'01/01/1'或NULL，则我将采用'sysdate'，否则我将只采用参数即'P_D_IN_END_DT'值。

SELECT
     CASE
          WHEN  P_D_IN_END_DT IN ( TO_DATE ('01/01/1900', 'dd/mm/yyyy'),  TO_DATE ('01/01/1', 'dd/mm/yyyy'),  NULL)
          THEN
             TRUNC(SYSDATE)
          ELSE
             P_D_IN_END_DT
       END 
       AS END_DT
FROM DUAL;

对于“01/01/1900”或“01/01/1”，工作正常。但是当我在参数中取NULL时，我不会得到sysdate，而是得到NULL

SELECT CASE
          WHEN NULL IN
                  (TO_DATE ('01/01/1900', 'dd/mm/yyyy'),
                   TO_DATE ('01/01/1', 'dd/mm/yyyy'), NULL)         
          THEN
             TRUNC(SYSDATE)
          ELSE
             NULL
       END
    AS END_DT
FROM DUAL;