Date difference in date in Oracle and Java

Question

following problem is bothering me and I can't find any reasonable explanation and a solution. Perhaps someone could enlighten me.

I have an application that calculates date difference (in days) - in a Search mask and in a Details mask. In the first mask I use days to filter out records with a duration search criteria (Search mask) and I do this with an SQL query:

WHERE...
...
AND DECODE(TRUNC(to_number(SUBSTR((close_date - 
create_date),1,instr(close_date - create_date,' ')))), NULL, 
TRUNC(to_number(SUBSTR((systimestamp - create_date),1,instr(systimestamp - 
create_date,' ')))), TRUNC(to_number(SUBSTR((close_date - 
create_date),1,instr(close_date - create_date,' ')))) ) >=140

AND DECODE(TRUNC(to_number(SUBSTR((close_date - 
create_date),1,instr(close_date - create_date,' ')))), NULL, 
TRUNC(to_number(SUBSTR((systimestamp - create_date),1,instr(systimestamp - 
create_date,' ')))), TRUNC(to_number(SUBSTR((close_date - 
create_date),1,instr(close_date - create_date,' ')))) ) <=140

In this special case I try to find out all the records that have a duration of 140 days.

In the second mask (Details) I show the record details, including its duration. This is done with the following java code:

public static Integer getDuration(Date caseDate, Date closeDate) {
    Date beginDate = caseDate;
    Date endDate = (closeDate != null)? closeDate: new Date();

    long difference = endDate.getTime() - beginDate.getTime();   
    int daysDiff = (int) (difference / (24.0 * 60 * 60 * 1000));  
    return new Integer(daysDiff);
}

My problem is that when I search, I find some records that do correspond to the search criteria. For instance I find 4 records and all of them have a duration of 140 days. That's according to Oracle. But when I open the Details mask for some of them I get a duration of 139 days for example. So somehow Java and Oracle calculate date differences in a different way. It seems that in Oracle some rounding is being made, but I can't find where this happens. So any suggestions would be helpful. Thanks!

Greets, almaak

Answer 1

The date could be the same but the time could be different. Resulting in 139 days when you calculate through milliseconds. (java)

I suggest not using millis but use the days to calculate.

Something like

public long daysBetween(Calendar startDate, Calendar endDate) {
   Calendar date = (Calendar) startDate.clone();
   long daysBetween = 0;
   while (date.before(endDate)) {
      date.add(Calendar.DAY_OF_MONTH, 1);
      daysBetween++;
   }}

or

/**
     *
     * @param c1 from
     * @param c2 to
     * @return amount of days between from and to
     */
    public int diff(Calendar c1, Calendar c2) {
        int years = c2.get(Calendar.YEAR) - c1.get(Calendar.YEAR);
        if (years == 0) {
            return c2.get(Calendar.DAY_OF_YEAR) - c1.get(Calendar.DAY_OF_YEAR);
        } else {
            Calendar endOfYear =  Calendar.getInstance();
            endOfYear.set(Calendar.YEAR, c1.get(Calendar.YEAR));
            endOfYear.set(Calendar.MONTH, 11);
            endOfYear.set(Calendar.DAY_OF_MONTH, 31);
            int days = endOfYear.get(Calendar.DAY_OF_YEAR) - c1.get(Calendar.DAY_OF_YEAR);
            for (int i=1;i <years;i++) {
                endOfYear.add(Calendar.YEAR, 1);
                days += endOfYear.get(Calendar.DAY_OF_YEAR);
            }
            days += c2.get(Calendar.DAY_OF_YEAR);
            return days;
        }
    }

Side note: The first example is slightly slower then the second, but if it's only for small differences it's neglectible.

Answer 2

I calculated this same way but I used dayDiff as long not as integer. So try it also, don't cast it. It should work fine.

Answer 3

The problem here is that you think both columns are DATE columns, where at least one of the two is really a TIMESTAMP column. When you extract one date from another, you get a NUMBER. But when you extract a date from a timestamp, or vice versa, you get an INTERVAL.

An example

A table with a DATE and a TIMESTAMP:

SQL> create table mytable (close_date,create_date)
  2  as
  3  select date '2010-11-01', systimestamp from dual union all
  4  select date '2010-11-11', systimestamp from dual union all
  5  select date '2010-12-01', systimestamp from dual
  6  /

Table created.

SQL> desc mytable
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 CLOSE_DATE                                         DATE
 CREATE_DATE                                        TIMESTAMP(6) WITH TIME ZONE

Extract a TIMESTAMP from a DATE column, leads to an INTERVAL:

SQL> select close_date - create_date
  2    from mytable
  3  /

CLOSE_DATE-CREATE_DATE
---------------------------------------------------------------------------
+000000130 11:20:11.672623
+000000140 11:20:11.672623
+000000160 11:20:11.672623

3 rows selected.

And there is no need to fiddle with TO_NUMBER's and SUBSTR's. Just use the EXTRACT function to get the component you want from an interval:

SQL> select extract(day from (close_date - create_date))
  2    from mytable
  3  /

EXTRACT(DAYFROM(CLOSE_DATE-CREATE_DATE))
----------------------------------------
                                     130
                                     140
                                     160

3 rows selected.

Regards, Rob.

And here is an example with two TIMESTAMPS and which shows that INTERVAL's are truncated, not rounded:

SQL> create table mytable (close_date,create_date)
  2  as
  3  select to_timestamp('2010-11-01','yyyy-mm-dd'), trunc(systimestamp,'dd') + interval '6' hour from dual union all
  4  select to_timestamp('2010-11-11','yyyy-mm-dd'), trunc(systimestamp,'dd') + interval '12' hour from dual union all
  5  select to_timestamp('2010-12-01','yyyy-mm-dd'), trunc(systimestamp,'dd') + interval '18' hour from dual
  6  /

Table created.

SQL> desc mytable
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 CLOSE_DATE                                         TIMESTAMP(9)
 CREATE_DATE                                        DATE

SQL> select close_date - create_date
  2    from mytable
  3  /

CLOSE_DATE-CREATE_DATE
---------------------------------------------------------------------------
+000000130 18:00:00.000000000
+000000140 12:00:00.000000000
+000000160 06:00:00.000000000

3 rows selected.

SQL> select extract(day from (close_date - create_date))
  2    from mytable
  3  /

EXTRACT(DAYFROM(CLOSE_DATE-CREATE_DATE))
----------------------------------------
                                     130
                                     140
                                     160

3 rows selected.