A simple expression can be a column, a constant, or NULL.

Column expression

A column expression refers to a column in a table by using its name, which can be either a fully qualified name or a simple name.

column_expression ::= [keyspace_name.][table_name.][column_name]

Constant expression

A constant expression represents a simple value by using literals.

constant_expression ::= string | number

NULL

When an expression, typically a column, does not have a value, it is represented as NULL.

null_expression ::= NULL