Difference between Expression

[zbaker]

I am looking for an expression that calculates the difference between two values, such as line 1 is the old item and line 2 is the new item. Any Ideas?


EX)

ID Start Date End Date Amount Difference
123 10/1/2011 10/1/2014 $100,000 0
123 10/2/2014 10/2/2015 $80,000 $20,000

[pbaldy]

Typically a subquery is used:

http://allenbrowne.com/subquery-01.html#AnotherRecord

[zbaker]

I understand how a subquery would work but i dont think any of the examples solve my issue of calculating the difference

[pbaldy]

I would think having the previous value on the same line would allow you to do "Old - New".

[aytee111]

Union query?