SQL: use WHERE clause in OVER()?

Question

How can I use WHERE clause to filter in the OVER clause?

i.e. from the following data

LoanID | Principal | Tenor | Amortizin         


        

Answer 1

If you're using SQL Server 2012, you'd be looking to specify ROWS/RANGE in your OVER:

Further limits the rows within the partition by specifying start and end points within the partition. This is done by specifying a range of rows with respect to the current row either by logical association or physical association. Physical association is achieved by using the ROWS clause.

Other database systems may have similar features. This feature is new in the 2012 version of SQL Server.