Expressions
Topics
An expression is a combination of one or more values, operators, or functions that evaluate to a value. The data type of an expression is generally that of its components.
Simple expressions
A simple expression is one of the following:

A constant or literal value

A column name or column reference

A scalar function

An aggregate (set) function

A window function

A scalar subquery
Examples of simple expressions include:
5+12 dateid sales.qtysold * 100 sqrt (4) max (qtysold) (select max (qtysold) from sales)