c# - Firebird group by period -

i pulling historical data firebird database below:

product_id     date     price 1           2001-01-01  10   1           2001-02-01  10 1           2001-03-01  15 1           2001-04-01  10 1           2001-05-01  20 1           2001-06-01  20 

what trying extract first occurrence every price change. example of expected data set:

product_id     date     price 1           2001-01-01  10   1           2001-03-01  15 1           2001-04-01  10 1           2001-05-01  20 

i know on mssql leverage lag that. possible firebird?

you can try this, aware didn't tested it:

create procedure sp_test returns (   product_id integer,   date date,   price integer ) declare variable last_product_id integer; declare variable last_date date; declare variable last_price integer; begin   select product_id, date, price       xxxx       order product_id, date       product_id, date, price   begin     if ((:last_product_id null) or          (:last_date null) or          (:last_price null) or          (:product_id <> :last_product_id) or         (:price <> :last_price))       suspend;     last_product_id = :product_id;     last_date = :date;     last_price = :price;   end;     end;