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Oracle Timestamp Elapsed Math

Oracle Database Tips by Donald Burleson

by Mike Ault

Getting Milliseconds from Oracle Timestamps

Had in interesting query from a client today. They have been storing start and stop times from a process in Oracle TIMESTAMP format and now want to get milliseconds out of the difference between the two timestamps. Seems pretty easy right?

OK, first we create a table with two TIMESTAMP columns and an index value:

SQL> select * from check_time
SQL> /
TIM_COL1                     TIM_COL2                     TIME_INDEX
---------------------------- ---------------------------- ----------
05-JUL-06 PM 05-JUL-06 PM          1
05-JUL-06 PM 05-JUL-06 PM          2

Now, if we were just using DATE we could subtract the dates and use the proper multiplier to convert the fractional return to the proper time unit. However when we subtract TIMESTAMPs:

SQL>  select tim_col2-tim_col1 from check_time;
+000000000 00:01:12.547000
+000000000 00:00:24.547000

We get a hideous time interval upon which you can't do math:

SQL> select sum(tim_col2-tim_col1) from check_time;
select sum(tim_col2-tim_col1) from check_time
ERROR at line 1:
ORA-00932: inconsistent datatypes: expected NUMBER got INTERVAL

So how to we capture milliseconds?

In steps the new interval functions that allow extraction of timestamp components, such as DAY, HOUR, MINUTE and SECOND…but wait there is no MILLISECOND! Of course a short trip to the documentation shows that the SECOND has a fractional component that allows us to specify the number of decimals after the second thus giving us access to the milliseconds, even down to microseconds in the interval value, look here:

SQL> select sum(
  2  (extract(hour from tim_col2)-extract(hour from tim_col1))*3600+
  3  (extract(minute from tim_col2)-extract(minute from tim_col1))*60+
  4* extract(second from tim_col2)-extract(second from tim_col1))*1000 ms from check_time
  5  /


Well, that is more like it! So now we can get the milliseconds between and do the aggregation functions such as sum() and avg() on the results.

Question:  After converting a timestamp into milliseconds and then adding some milliseconds in that value, Can we convert those milliseconds into a new timestamp?

Answer: This code will add milliseconds to a TIMESTAMP datatype:

   to_char(systimestamp,'dd-mm-yyyy hh24:mi:ss.FF') as ts,
      to_char(sysdate,'dd-mm-yyyy hh24:mi:ss.')
         ) + 250),'dd-mm-yyyy hh24:mi:ss.FF'
   ) as ts_1
from dual;


Also see here for an example of inserting milliseconds into a column.  Start by defining column COL1 with datatype timestamp;

insert into
   temp_table (COL1)
   (timestamp '1999-12-01 11:30:55.3');

SQL> select col1 from temp_table;

01-DEC-99 AM

If you like Oracle tuning, you may enjoy the new book "Oracle Tuning: The Definitive Reference", over 900 pages of BC's favorite tuning tips & scripts. 

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