About SQL Data Types

When you create a table, you must specify the SQL data type for each column. The data type of a column determines what values the column can contain. For example, a column of type DATE can contain the value '01-MAY-05', but it cannot contain the numeric value 2 or the character value 'shoe'. SQL data types fall into two categories: built-in and user-defined. (PL/SQL has additional data types—see "About PL/SQL Data Types".)