PostgreSQL, Second Edition

Expression Evaluation and Type Conversion

Now that you have seen all the standard PostgreSQL data types, it's time to talk about how you can combine values of different types into complex expressions.

First, you should understand that an expression represents a value. In a well-designed language, you can use an expression anywhere you can use a value. An expression can be as simple as a single value: 3.14159 is an expression. A complex expression is created by combining two simple expressions with an operator. An operator is a symbol that represents some sort of operation to be applied to one or two operands. For example, the expression “customer_balance * 1.10 ” uses the multiplication operator (*) to multiply customer_balance by 1.10. In this ...