Something I’ve occasionally thought would be really nice is if Oracle had a good way of summing up interval data types, much the same way that you can SUM() number data types. Occasionally I’ve designed processes that record start and stop timestamps of operations. If you want to know how long the operation lasted, you could do the end timestamp minus the start timestamp to get a DAY TO SECOND INTERVAL data type.
select end_timestamp - start_timestamp as job_duration
If I want to know the total runtime of a set of operations, there’s not a nice, slick, easy way to do this.
Usually, I get away with some jankedy code like this:
cast(end_timestamp as date) - cast(start_timestamp as date)
, 'DAY') duration
First, you gotta cast the timestamps as dates (meaning you lose any fractional-seconds).
Then you subtract the start date from the end date. That gives you a number, which represents the number of days (possibly fractional).
Oracle then allows you to sum up those numbers.
If you want the number back in interval format, you can supply it to a NUMTODSINTERVAL() function, passing in ‘DAY’ as the second argument.
It sucks, it’s not smooth, it loses precision, the maintaining developer has to double-take to try to figure out what it is that I’m doing. Wouldn’t it be nice if there was some smooth way to just add up intervals?
Well, after giving it some thought, I decided to create my own…