Sql Excel : What Is a Table?

Each zip code also has an area, measured in square miles and recorded in the
landsqmi column. This column contains a number, and the database does not
know what this number means. It could be area in acres, or square kilometers, or
square inches, or pyongs (a Korean unit for area). What the number really means
depends on information not stored in the tables. The term metadata is used to
describe such information about what the values in columns mean. Similarly,
fipco is a numeric value that encodes the state and county, with the smallest value
being 1001, for Alabaster County in Alabama.
Databases typically have some metadata information about each column.
Conveniently, there is often a label or description (and it is a good idea to fill this
in when creating a table). More importantly, each column has a data type and a
flag specifying whether NULL values are allowed. The next two sections discuss
these two topics because they are quite important for analyzing data.