SQL Server 2008: updating and keeping tracking of anuual price increase -

i have project right need update prices list of products. prices 1/1/2007 12/31/2011 given , need increase prices 5% each year, until end of 2015.

here have. getting stuck on updating prices (ie 5% increase). keep getting error message duplicate data. in advance help/hints !

error message:

msg 2627, level 14, state 1, procedure update_history, line 9
violation of primary key constraint 'pk_pricecha_207f7de23a81b327'. cannot insert duplicate key in object 'dbo.pricechange_history'.

tables:

create table pricechange (productid integer not null primary key,  startdate date,  endingdate date,  unitprice money);   alter table pricechange add foreign key (productid) references product(productid)   create table pricechange_history (history_productid integer not null primary key,  history_startdate date,  history_endingdate date,  history_unitprice money,  modified_date datetime,  changetype varchar(20) );  alter table pricechange_history  add foreign key (history_productid) references product(productid) 

triggers

create trigger [insert_history] on pricechange insert       insert pricechange_history (history_productid, history_startdate,                                  history_endingdate, history_unitprice,                                 modified_date, changetype)         select              productid, startdate, endingdate, unitprice,             getdate(), 'inserted'         inserted  create trigger [update_history] on pricechange update    insert pricechange_history(history_productid, history_startdate,                               history_endingdate, history_unitprice,                               modified_date, changetype)        select             productid, startdate, endingdate, unitprice,            getdate(), 'before update'        deleted     insert pricechange_history(history_productid, history_startdate,                               history_endingdate, history_unitprice,                               modified_date, changetype)       select                productid, startdate, endingdate, unitprice,           getdate(), 'after update'       inserted 

insert + update

insert pricechange  values(1,'1/1/2007', '12/31/2011', 500) <---  record query both pricechange , pricechange history  update pricechange  set unitprice = (unitprice * 1.05),     startdate = '1/1/2012',     endingdate = '12/31/2012'       productid = 1  update pricechange  set unitprice = (unitprice * 1.05),     startdate = '1/1/2013',     endingdate = '12/31/2013'       productid = 1  update pricechange  set unitprice = (unitprice * 1.05),     startdate = '1/1/2014',     endingdate = '12/31/2014'       productid = 1  update pricechange  set unitprice = (unitprice * 1.05),     startdate = '1/1/2015',     endingdate = '12/31/2015'      productid = 1 

price_history has pk on productid cannot have duplicate products. add identity primary key.