It's very important to enable end users to compare the business performance with previous time periods. By achieving this, end users will understand the business better. Business users need to make these comparisons across multiple time periods.
For example, let's assume that business users are asking for the sales amount of this month and the sales amount for last month. Most probably, they're looking forward to comparing these two values and seeing the difference. Here is one method:
Calculate the sales amount of this month: This can be achieved by one query
Calculate the sales amount of last month: This is another query
Calculate the difference between these months: This will be the last query
As you see, we'll need at least three queries. There's another solution in Oracle Business Intelligence Enterprise Edition. It's time series functions. There are three types of time series functions: