Updating

1. Updating allows us to change some values in a tuple without necessarily changing all.

   We use the update operator, , with the form

   

   where is a relation with attribute , which is assigned the value of expression .

   The expression is any arithmetic expression involving constants and attributes in relation .

   Some examples:

   1. To increase all balances by 5 percent.

   

   This statement is applied to every tuple in deposit.

   2. To make two different rates of interest payment, depending on balance amount:

   

   Note: in this example the order of the two operations is important. (Why?)