Use NOT EXISTS
select
v.Id,
v.MissingVehicleFlag,
v.Make,
v.OatsModelId,
v.Model,
v.PersonalisedName,
v.RegistrationPlate,
v.ImageUrl,
v.ImageCropStartingX,
v.ImageCropStartingY,
v.LastModified,
v.Account_Id,
v.Deleted
from RobbinsuatLatest.dbo.Vehicles v
where NOT EXISTS (
select v2.Id
from RobbinsuatLatest.dbo.VehiclesV2 v2
WHERE v.Id = v2.Id
)
And make sure there is an index on Id
in both RobbinsuatLatest.dbo.Vehicles
and RobbinsuatLatest.dbo.VehiclesV2