Although the syntax is different, you can achieve exactly what you want.
You can create type by using the script below;
CREATE TYPE tr_del AS (row_id varchar(18), pk_id integer);
Then your table structure should look like this;
CREATE TABLE employees (
After that you can use it in the query like this;
(any_field_name).row_id AS last_name,
(any_field_name).pk_id AS employee_id
department_id = 30;
Fiddle is here
You may want to read Composite Types section.