When you create a table in PostgreSQL, you specify the type of data that you will store in each column. For example, if you are storing a customer name, you will want to store alphabetic characters. If you are storing a customer's birth date, you will want to store values that can be interpreted as dates. An account balance would be stored in a numeric column.
Every value in a PostgreSQL database is defined within a data type. Each data type has a name (
CHARACTER, and so on) and a range of valid values. When you enter a value in PostgreSQL, the data that you supply must conform to the syntax required by the type. PostgreSQL defines a set of functions that can operate on each data type: ...