Sql Query or .net code

Question

Hi,

I have one transaction table. in that one OrderId column is there. for that column assign one default value like 'BC10'. I need to increment that OrderId value for every transaction. how can i write query for that or is there any possibility to increment that column value from aspx page. if anyone knows pleae help me......

Example: i have done first transaction, that OrderId is BC10. For next transaction OrderId is BC11.