Hi all, I am new to the forum~

Suppose I have multiple tables, T1, T2, T3. I will use SELECT queries and apply AVG() and STDEV() on each of their columns, and average their results.

I can do this in two ways: one is to apply my SELECT multiple (3) times, then divide it by 3 in this case.

Another way is I create a View that UNIONS all T1 T2 T3, and apply AVG() and STDEV() on each columns.

Which solution is better? I mean, from a performance point of view. This is just a simplified version of my problem, and I would like to know what is the performance of using one (View) over the other (Table)... Does using View instead of table give me any performance overhead? Thanks everyone...

They are the same solution. whether you use a select statment or a veiw you will be pulling data off the drives (or cache) to produce the answer. The view has the advantage of being pr-optimized. Views are generally used for this type of thing as it hides all the aggregation.

Don't know if this helped, Books Online has some interesting info look up views-SQL Server, overview and follow the hyper link to Scenarios for Using Views.