Required attributes and null values

- [Instructor] When entering records into a database, … it's not a requirement that every … attribute column is populated with data. … When a value isn't supplied, it's said to be null. … A null value represents data that's unspecified, … unknown, or not applicable. … It's important not to confuse null with zero, … or a blank space character. … Null means literally nothing at all or no data. … Let's take a look at this data table … of people and their birthdays. … Antonio's birthday is currently null. … That doesn't mean that he doesn't have a birthday. … He most certainly does. … All we can say about it is that it's currently not known, … and any information about it is missing from the database. … Null values are important when you start thinking about … whether information in a column … is required to be supplied for every record. … Maybe this data table represents customers … and you've offered to send a special coupon … to people on their birthday. … Some customers will give you that information …