Question :
I am dealing with large amount of data approx 1 million rows with 100s of columns.
I have this proc which performs some calculation over this data based on grouped by a colum1.
Now the same calculation is performed over this data grouped by column1, column2.
I can optimise the whole operation by creating indexes on column1 and column2.
But how i can achive the performance if column1 or column2 are dynamic and up to nth column.
Example:
For n columns the group by operation is going to be like as follows
operation 1 : group by column1
Operation 2 : group by column1, column2
Operation n : group by column1, column2….. upto columN
Answer :
If you need all those aggregates at once use ROLLUP or GROUPING SETS to calculate multiple aggregate grains in a single scan.
If you want to optimize a large table for many different aggregates use a Columnstore index.