Selecting Nested Fields

When the ROW type that defines a column itself contains other ROW types, the column contains nested fields. Use dot notation to access these nested fields within a column.

For example, assume that the address column of the employee table contains the fields: street, city, state, and zip. In addition, the zip field contains the nested fields: z_code and z_suffix. A query on the zip field returns values for the z_code and z_suffix fields. You can specify, however, that a query returns only specific nested fields. The following example shows how to use dot notation to construct a SELECT statement that returns rows for the z_code field of the address column only: 
SELECT address.zip.z_code 
   FROM employee;