Question

I am wondering if it is possible to innner join on the greates value.

So for example

SELECT *
FROM Vehicle v
INNER JOIN VehicleCost vc ON v.VehicleWeight > vc.WeightFrom AND c.VehicleWeight < vc.WeightTo

But if v.VehicleWeightTotal > v.VehicleWeight I want that to replace v.VehicleWeight on the inner join. So potentially this could be a different join for each vehicle.

How would I go about doing that check within the join?

Sample:

tblVehicle
VehicleId  VehicleWeight VehicleWeightTotal 
1               12              15
2               1               8
3               16              20

tblVehicleCost
WeightFrom    WeightTo  Dollars
0               5         1
6               11        8
12              16        9 
17              20       15

So:

Vehicle 1 = 9
Vehicle 2 = 8
Vehicle 3 = 15

Answer 1

Your requirements can be more simply expressed as:

use the greater of VehicleWeight and VehicleWeightTotal when joining

This is how you express that in SQL:

SELECT *
FROM Vehicle v
INNER JOIN VehicleCost vc 
   ON (case
         when VehicleWeightTotal > VehicleWeight then VehicleWeightTotal
         else VehicleWeight
       end) between vc.WeightFrom AND vc.WeightTo;

I took the liberty of changing your range check to use between, but if it’s not OK to match on the value equalling the range limits – ie using >= and <= in your query – then just repeat the case statement for each side of the range.