PL/SQL Add Column

Table Students

STUDENT_ID FIRST_NAME LAST_NAME GENDER CITY
1 Daniel SCOTT M New York
2 Anthony SIMMONS M Chicago
3 Sophia THOMPSON F Los Angeles

Add single column to table

ALTER TABLE STUDENTS 
  ADD country VARCHAR2(150);

Add columns to table

ALTER TABLE STUDENTS 
  ADD ( address VARCHAR2(4000),
        country VARCHAR2(150)
      );

Query the table

SELECT STUDENT_ID, FIRST_NAME, LAST_NAME, ADDRESS, COUNTRY FROM STUDENTS; 
STUDENT_ID FIRST_NAME LAST_NAME ADDRESS COUNTRY
1 Daniel SCOTT
2 Anthony SIMMONS
3 Sophia THOMPSON