如何在oracle中将sysdate月的值转换为数字？

Question

Im trying to return the CARDS of my CARD table that will expire in the next month. But the problem is that the table has two columns to represent the card date. The columns are EXPIREDAY and EXPIREMONTH ,both are numbers. So when i do that query i get an error:

   select * from CARD WHERE EXPIREDAY <= sysdate - interval '2' DAY;
   //Oracle error: ORA-00932: inconsistent datatypes: expected NUMBER got DATE

Is there a way to convert the sysdate - interval '2' DAY as Number data type?

Thanks!

Answer 1

If you want to compare the values as strings you can use this to convert the SYSDATE

SELECT TO_CHAR(sysdate, 'MM') || TO_CHAR(sysdate, 'DD') MONTH_NUM FROM DUAL
-- gives you "0922"

and this for your numeric columns which will pad with leading zeros if you only have a single digit

SELECT TO_CHAR(9, 'FM00') || TO_CHAR(22, 'FM00') MONTH_NUM FROM DUAL
-- also gives you "0922"

If you have control over the table schema it would be best practise to store both the DAY and MONTH values in a single numeric field, so that 9-SEP would be stored in this column as the numeric value 0922 where the month is first so that the natural ordering is used.

Answer 2

A simple and not necessarily very efficient approach is to convert the day and month values into an actual date, using to_date() , and then compare that with your target date range:

select * from card
where to_date(lpad(expireday, 2, '0')
  ||'/'|| lpad(expiremonth, 2, '0'), 'DD/MM')
between sysdate and add_months(sysdate, 1);

Which appears to work . But this will have problems if the dates span the end of the year. Because your table doesn't specify the year, you either have to work one out, or allow to_date to default it to the current year. And if you let it default then it won't work. For example, if you have values for December and January in your table, and run this query in December, then the January dates will be seen as January 2014, and won't be counted as being in the next month. So you'll need to do more to pick the right year.

This treats any month numbers before the current one as being next year, which may be good enough for you as you only have a one-month window:

select * from card
where to_date(lpad(expireday, 2, '0')
  ||'/'|| lpad(expiremonth, 2, '0')
  ||'/'|| (extract(year from sysdate) +
    case when expiremonth < extract(month from sysdate) then 1 else 0 end),
    'DD/MM/YYYY')
between sysdate and add_months(sysdate, 1);

SQL Fiddle using a date range from December to January.

And you can see the ways the two columns are being combined to form a date in this Fiddle .

As so often, the moral is... store things as the right data type. Store dates as dates, not as string or numbers.

Answer 3

Im trying to return the CARDS of my CARD table that will expire in the next month. But the problem is that the table has two columns to represent the card date.

Assuming:

1. you are using floating months (say: from 23 dec. to 23 jan.) and
2. your table somehow only contains one (floating ?) year of data

Why can't you use simple arithmetics? Like that:

-- some constant definitions for testing purpose
with cst as (
  select EXTRACT(DAY from TO_DATE('23/12','DD/MM')) as theDay,
         EXTRACT(MONTH from TO_DATE('23/12','DD/MM')) as theMonth
  from dual)

-- the actual query
select card.* from card,cst 
  where (expiremonth = theMonth AND expireday > theDay)
     or (expiremonth = 1+MOD(theMonth,12) AND expireday <= theDay);
  --                   ^^^^^^^^^^^^^^^^^^
  --            map [01 .. 12] to [02 .. 12, 01] (i.e.: next month)

This will simply select all "pseudo-dates" from tomorrow to the end of the month, as well as any one before (and including) the current day# next month.

See this example .

---

For something a little bit more generic, but probably more efficient than converting all your values TO_DATE , you might want to try that:

-- the calendar is the key part of the query (see below)
with calendar as (
  select extract(month from sysdate + level) as theMonth,
         extract(day from sysdate + level) as theDay
    from DUAL connect by ROWNUM <= 8)
--                                 ^
--              adjust to the right number of days you are looking for
select card.* from card join calendar
  on expiremonth = theMonth and expireDay = theDay

The idea here is to simply build a calendar with all the upcoming days and then join your data table on that calendar. See an example here .

Answer 4

Try using to_char(sysdate - interval '2' DAY,'ddmmyyyy') to convert to character type. The date format('ddmmyyyy') will depend of the value of expiredate