how to add the two column values in sql code example

Example 1: add multiple field in table sql

ALTER TABLE employee
  ADD (
  	  last_name VARCHAR(50) NOT NULL,
      first_name VARCHAR(40) NOT NULL
      );

Example 2: add multiple columns to table sql

ALTER TABLE table_name
  ADD column_1 column_definition,
      column_2 column_definition,
      ...
      column_n column_definition;