Subject Re: [firebird-support] How to add previous column value to current value?
Author Michal Kurczabinski
Post date 2016-04-04T18:57:21Z
Try this:

select t.name, t.data, coalesce(t.data -(select data from t1 d where d.id = t.id -1),0) from t1 t

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regards,
Michał Kurczabiński