How to create simple insert trigger

I have just one table but need to create a trigger that takes place after an update on the Orders table. I need it to multiply two columns and populate the 3rd column (total cost) with the result as so:

Orders

ProductPrice ProductQuantity TotalCost
-- --
￡2.50 2
￡1.75 3
￡12.99 2

Can anyone please help me?You don't need a trigger, you need a computed column:

CREATE TABLE [dbo].[xxx](
[col_a] [int] NOT NULL default(2),
[col_b] [int] NOT NULL default(2),
[col_axb] as a * b,
) ON [PRIMARY]
GO|||Thank you for the help!