Simple expressions

A simple expression can be a column, pseudocolumn, constant, sequence number, or null value.

In addition to user schemas, schema can also be PUBLIC to specify the attribute of a synonym for a table or a view. You can use PUBLIC to specify a public synonym in only a DML statement. You cannot use PUBLIC in a DDL statement. NCHAR and NVARCHAR2 are not valid pseudocolumn data types.

The following list provides some valid simple expressions:

• employees.last_name

• 'this is a text string'

• 10

• N 'this is an NCHAR string'