Expressions and derived values

You are not limited to selecting columns by name. You can list an expression in the Projection clause of a SELECT statement to perform computations on column data and to display information derived from the contents of one or more columns.

An expression consists of a column name, a constant, a quoted string, a keyword, or any combination of these items connected by operators. It can also include host variables (program data) when the SELECT statement is embedded in a program.