Teradata Date Time Part 13 -- Adding two TIMES is illogical

• We know can we can subtract two times to get the difference between two point in times. The result is an interval.

Example:

SELECT (TIME '12:12:13' - TIME '11:11:11') MINUTE

Result is 61 .

The output is INTERVAL MINUTE

• We can add/subtract an interval to a Time to get another point of time as the result

SELECT TIME '12:11:11' + INTERVAL '11' MINUTE

Result is 12:22:11

The data type of the result is TIME.

Ever wondered what would be the result of following query : SELECT TIME '12:12:13' + TIME '11:11:11'

Well , I wondered and experts called it as illogical :)

There is nothing called addition of two TIME's. It does not symbolize anything.

We add Interval to a Starting time to get the end time.

Adding two dates is also illogical , however adding two dates does not fail.

We get a result which is an integer.

We know that date are saved internally as integers, the result is actually the sum of two integers.

select date '2012-12-12' + date '2011-12-12';

Result : 1469944

I asked the same question on a forum and following is the nice reply i received from a contributor:

Another way to look at it: a TIME is a point (0 dimensions); an interval is
a line (1 dimension).
 
You can:
- find the distance between two points (time - time);
- construct a line beginning at a point (time + or - interval);
- place one line at the end of another (interval + interval);
- find the difference in length of two lines (interval - interval).
 
You cannot add two points (time + time).