Updating Data
Data can be updated using a similar syntax to that of the INSERT statement. Consider an example:
UPDATE customer SET email = lower(email);
This replaces the string values of all email attributes with the same string in lowercase. The function lower( ) is one of many functions discussed later in Section 3.9.
The UPDATE statement is also often used with the WHERE clause. For example:
UPDATE customer SET title = 'Dr' WHERE cust_id = 7;
This updates the title attribute of customer #7. Consider a second example:
UPDATE customer SET zipcode = '3001' WHERE city = 'Melbourne';
This updates the zipcode of all rows with a city value Melbourne.