Question

如何在Oracle 9i的where条件中使用计算列？

我想使用像

这样的东西

select decode (:pValue,1,
               select sysdate from dual,
               select activation_date from account where AcNo = 1234) as calDate
where caldate between startDate and endDate;

Answer 1

您可以使用内嵌视图：

select calcdate from
(
select startDate, endDate,
       decode (:pValue,1,
               select sysdate from dual,
               select activation_date from account where AcNo = 1234) as calcdate
)
where calcdate between startDate and endDate;

Answer 2

您可以从双重选择日期并加入结果：

select * 
from   <<your table with startDate and endDate columns>> -- Since you ommited the main "from" clause from your statement
,      (
         select decode( :pValue
                      , 1, sysdate
                      , ( select activation_date from account where AcNo = 1234 )
                      ) as calDate
         from   dual
       ) c
where  c.calDate between startDate and endDate
... -- any other conditions you may need

如何在哪里条件下使用计算列？

2 个答案: