Update records in a table in a process

Table with 2 fields :
Name : Plain text
Period : Number

I want to update (increase) field “period” by 1
In SQL : UPDATE person SET period = period + 1 WHERE period > 2017

I expect :
FIND Persoon WHERE Persoon.Period > 2017
Persoon.Period=Persoon.Period + 1

But this doesn’t work properly, all selected records are updated to the same value.

So I used an extra : IN BATCHES OF 1
FIND Persoon WHERE Persoon.Periode > 2017 IN BATCHES OF 1
Persoon.Periode=Persoon.Periode + 1

It worked but I guess it will be very slow when there are many records.

Have sent you a sample bsv on Skype Jannes