Oracle get all records between current day inserted with timestamp - oracle

Question

Unable to retrieve records properly with the formatted date values, need select query with right date format to get all records inserted per day
I have a date string like this in my script -  
dateString :='26-MAR-20 05.00.00.00000000 AM';
I want to add 0.313 minutes to this date value. And also I want to
increment it to the next day something like this- '27-MAR-20
05.00.00.00000000 AM'; ​
I tried this 
dateString :='26-MAR-20 05.00.00.00000000 AM';
dateString :=to_char(dateField,'DD-MON-YYYY HH24:MI:SS.FF');
dateField := to_timestamp(dateString, 'DD/MON/YYYY HH24:MI:SS.FF') + 0.313 * INTERVAL '1' MINUTE;
​
I can see the output and inserted these values into the DB but
unable to retrieve records properly with these formatted date values..
I suspect it might be to do with the timestamp fields
When I run this query -
select *from rptallexceptions where exceptiontime between '27-MAR-2020 04.00.00.000000000 AM' and '28-MAR-2020 03.59.00.000000000 AM' order by exceptiontime desc;
​
--- this one gives 3833 records but expected is 4600
it shows only the records on 27th march., records inserted with timestamp containing 28th march are not retrieved..
select *from rptallexceptions where exceptiontime between '28-MAR-2020 04.00.00.000000000 AM' and '29-MAR-2020 03.59.00.000000000 AM' order by exceptiontime desc;
--- this one returns '0' rows
Excerpt from the script:
cnt :=cnt +1;
dateString :=to_char(dateField,'DD-MON-YYYY HH24:MI:SS.FF');
-- add time difference for each exception.
dateField := to_timestamp(dateString, 'DD/MON/YYYY HH24:MI:SS.FF') + 0.313 * INTERVAL '1' MINUTE;
-- after n*4600 exceptions,update date to next date.
IF REMAINDER(cnt,exceptionsPerDay) = 0 THEN
dateField := to_timestamp(dateField + 1,'DD/MON/YYYY HH24:MI:SS.FF');
END IF;

Answer 1

The way I see it, your problem is that you're comparing timestamps to strings.
Sample table:
SQL> create table test as
2 select to_timestamp('27.03.2020 04:00:00:000000', 'dd.mm.yyyy hh24:mi:ss:ff6') datum, 'A' name from dual
3 union all
4 select to_timestamp('28.03.2020 15:23:00:000000', 'dd.mm.yyyy hh24:mi:ss:ff6') datum, 'A' name from dual;
Table created.
Query should use timestamp, not string:
SQL> select *
2 from test
3 where datum between to_timestamp('25.03.2020 12:00:00:000000am', 'dd.mm.yyyy hh:mi:ss:ff6am') --> timestamp
4 and to_timestamp('28.03.2020 12:00:00:000000am', 'dd.mm.yyyy hh:mi:ss:ff6am'); --> timestamp
DATUM N
--------------------------------------------------------------------------- -
27.03.20 04:00:00,000000000 A
SQL>
You were kind of "lucky" (though, one might call it bad luck as your query didn't fail, but it produced wrong results, according to number of rows being returned) for not getting an error as my database raises (due to different NLS settings):
SQL> select *
2 from test
3 where datum between '25.03.2020 12:00:00:000000am' --> string
4 and '28.03.2020 12:00:00:000000am'; --> string
where datum between '25.03.2020 12:00:00:000000am'
*
ERROR at line 3:
ORA-01830: date format picture ends before converting entire input string
SQL>
Strings are handled differently than dates (or timestamps), or numbers. Maybe you'll see the difference clearly in this example:
SQL> with test (col) as
2 (select '1' from dual union all
3 select '9' from dual union all
4 select '20' from dual
5 )
6 select *
7 from test
8 where col < '9';
CO
--
1
20
SQL>
20 < 9? Yes, if those are strings. The same might have happened to you. Try with proper datatype.

Answer 2

When you do:
dateString :=to_char(dateField,'DD-MON-YYYY HH24:MI:SS.FF');
you are converting whatever is the initial value of dateField to a string; but it looks like that has has not been set yet, so you end up with an empty string (which is the same as null). Your original value of dateString is never being used.
If you skip that and just do:
dateString :='26-MAR-20 05.00.00.00000000 AM';
dateField := to_timestamp(dateString, 'DD/MON/YYYY HH24:MI:SS.FF') + 0.313 * INTERVAL '1' MINUTE;
​then you are converting the 2-digit year 20 with a YYYY format element, which will turn it into year 0020, not 2020; but you also don't have AM in the format model, so it will get ORA-01830 anyway, and have HH24 instead of HH. I think your to_char() is attempting to 'correct' the string format, but that's not a great approach.
If you can't control the starting string format then the model has to match that:
dateString :='26-MAR-20 05.00.00.00000000 AM';
dateField := to_timestamp(dateString, 'DD-MON-RR HH:MI:SS.FF AM') + 0.313 * INTERVAL '1' MINUTE;
which gives dateField a value of 2020-03-26 05:00:18.780000.
Later on you do:
dateField := to_timestamp(dateField + 1,'DD/MON/YYYY HH24:MI:SS.FF');
which is also doing an implicit conversion of dateField + 1 - which is converted to a date, incidentally as timestamp + number is a date, not a timestamp - to a string; which will use your NLS_DATE_FORMAT. Presumably that is something like 'DD-MON-YYYY'.
So stepping through that:
dateField + 1 => date '2020-03-27 05:00:18' (losing fractional seconds)
implicit to_char(dateField + 1) => string '27-Mar-2020' (losing time)
to_timestamp(to_char(dateField + 1), '...') => timestamp '2020-03-27 00:00:00.000000' (with time at midnight).
So your between is, at best going to find records between 2020-03-26 05:00:18.780000 and 2020-03-27 00:00:00.0000000 - so it won't pick up any records later than midnight on the 27th.
Don't convert to and from strings when you don't need to; leave data in its native data type (timestamp in this case) and use direct manipulation with intervals.
Using between isn't ideal anyway, because it is inclusive; it would be better to end up with:
exceptiontime >= timestamp '2020-03-26 05:00:18.780000'
and exceptionTime < timestamp '2020-03-27 05:00:18.780000'