I have designed a database but need support on the following:

* within the same table

* subtract the current record from the last record

* but only from matching fields in the first column

for example:

Table

Field 1        Field 2    Field 3

Vehicle       Cost        Difference from last Vehicle (Car) Cost

Car              $100      0

Car              $150      $50

Truck           N/A

Bicycle        N/A

Car              $350       $200 

I found this in the Help Line but it subtracts the last field without differentiating by the first column

let me := this;
'spend' - last((select 'TableName' where number(_id) < number(me._id)) order by number(_id)).'spend'

Gruss aus Amerika.  Ich wunsche euch einen guten Rutsch ins neue Jahr.