SQL adding two columns (datetime) <p>I have two columns that contains datetimes and i need two add them together somehow. I've tried using sum but that didnt work. Im using sqlserver 2008.</p> <p><strong>Columns</strong></p> <p><strong>loanPeriod</strong> = the loanperiod of the item </p> <p><strong>checkOutDate</strong>= when the item was borrowed</p> <p>And Im trying to achieve this lastreturndate = (checkoutDate + loanperiod)</p>