shows value and previous year

[Anonymous]

I would like to know how it shows value and previous year columnar

I have the Year 2017 and 2018 one on each line and both have the same destination and origin and also have freight value I will try to draw

<YEAR> ORIGIN> DESTINATION> FREIGHT VALUE> DIF ANO>

<2017> SP> MG> R $ 5000.00> 0>

<2018> SP> MG> R $ 3000.00> R $ 2000.00>

That if you had 2016 showed the difference between 2016 and 2017 also in the future will show years 2017 2018 2019 2020

I wanted this "DIF ANO" to be an expression without variable all leave the same table

Shipping Table: fields: Year, Origin, Destination, Value Freight.

This freight value is already = SUM (VALUE_FRETE) has many deliveries for those origin and destination and each origin and destination that I selected if it had delivery in two years showed that difference.

Thankful