Tuning average of a data set calculation in an increasing Data Set

Question

I was asked a question by one of my colleagues in another team:
In a table with increasing number of rows and that too in an increasing order of Id Keys- 1,2, ....3000... 12000 .... 50000..............
We have a column age.
And we have a query:
select avg(age) from <tablename> ; 
This query is increasingly taking a longer time
How to optimize it.
I guessed that we might need some  sort of partitioning or additional grouping but I am not fully sure
as to that would be the best solution.
What do you say?

Answer 1

I was asked a question by one of my colleagues in another team:
In a table with increasing number of rows and that too in an increasing order of Id Keys- 1,2, ....3000... 12000 .... 50000..............
We have a column age.
And we have a query:
select avg(age) from <tablename> ;
This query is increasingly taking a longer time
How to optimize it.
I guessed that we might need some  sort of partitioning or additional grouping but I am not fully sure
as to that would be the best solution.
What do you say?
I say it sounds like an interview question to me!
A question like that is often ask to see how (or if) a person thinks before answering.
Will they just blindly try to privide an answer?
Are they willing to ask questions to clarify the question being ask?
Will they ask questions to try to understand the actual requirements?
1. No one stores AGE in a database. Someone's age changes everyday so 'age' is a total meaningles piece of data. A data element like 'age at death' is meaninful and does NOT change. It can be meaningful because it protects potentially sensitive information like birth date and death date.
2. Neither the questioner nor you have presented ANY INFO indicating that any query needs to be optimized. Of course a query on an increasing amount of data will take an 'increasingly' longer amount of time. That should be obvious. If someone asks you to count to 100 won't  that take MORE TIME than counting to 95?
3. A simple query like 'SELECT AVG(age)' does NOT need to be optimized - certainly not based on any info you provided. That AVG function may be part of a larger, more compliex, query and maybe that 'other' query needs to be tuned.
Your 'colleague' is either 'testing' you or 'playing' with you.
If it ain't broke, don't fix it.
The first step is to VERIFY that a problem actually exists. That means test and get PROOF that the query is taking longer than before and measure HO MUCH longer it is taking. As noted above if there is more data then a query MUST TAKE LONGER - that is a simple fact. That doesn't mean there is any tuning to be done.
Only after you verify that a problem actually exists do you start looking for solutions.