Question

Basically I have an invoice lines for a below account as below:

BillID     AccountID     BilledFrom        BillTo      Days     Price
 38         3456         10/10/2012       10/11/2012    30       86p
 39         3456         11/11/2012       11/12/2012    30       87p
 40         3456         12/12/2012       30/12/2012    18       81p

The user would like to refund the customer for a partial date Range, therefore the user will need to enter a date from and date to date:

Date From: 18/10/2012     DateTo: 14/12/2012

This will cause credit lines to refund the client working out the days and price for each line. I need to return each line and show the cut off points. As you can see the ranges entered span across the 3 invoice lines.

The result needed is:

BillID  AccountID  BilledFrom    BillTo     RangeStart  RangeEnd    Days  Price
 38       3456     10/10/2012   10/11/2012  18/10/2012  10/11/2012   22    86p
 39       3456     11/11/2012   11/12/2012  11/11/2012  11/12/2012   30    87p
 40       3456     12/12/2012   30/12/2012  11/11/2012  11/12/2012    2    81p

The results basically will bring back the initial applicable invoice line but work out how this range fits and calculates the days against the bill from and bill to from the date range entered.

I need a function either in SQL to provide this result. Any Help would be appreciated. Thank you in advance.

Answer 1

try this:

  declare @DateFrom date='10/18/2012'     
 declare @DateTo date='12/14/2012'

 select T.BillID,T.AccountID,T.BilledFrom,T.BillTo,
     case when BilledFrom<@DateFrom then @DateFrom else BilledFrom end [RangeStart], 
     case when BillTo<@DateTo then BillTo else @DateTo end [RangeEnd],DATEDIFF(D,case when BilledFrom<@DateFrom then @DateFrom else BilledFrom end ,case when BillTo<@DateTo then BillTo else @DateTo end ) [Days],Price
     from t_account  T

SQL Fiddle Demo