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SQL>
SQL> create table people(
2 employee_id number(9),
3 first_name varchar2(15),
4 last_name varchar2(20),
5 email varchar2(25),
6 constraint pk_people primary key (employee_id)
7 );
Table created.
SQL>
SQL> insert into people values (1, 'T', 'Kyte', 'YourName@q.com');
1 row created.
SQL>
SQL> insert into people values (2, 'S', 'Viper', 'sdillon@q.com');
1 row created.
SQL>
SQL> insert into people values (3, 'C', 'Beck', 'clbeck@q.com');
1 row created.
SQL>
SQL> commit;
Commit complete.
SQL>
SQL> select * from people;
EMPLOYEE_ID FIRST_NAME LAST_NAME EMAIL
----------- --------------- -------------------- -------------------------
1 T Kyte YourName@q.com
2 S Viper sdillon@q.com
3 C Beck clbeck@q.com
SQL>
SQL>
SQL> alter table people
2 add (
3 ssn number(9)
4 );
Table altered.
SQL>
SQL> update people set ssn = 123456789 where employee_id = 1;
1 row updated.
SQL>
SQL> update people set ssn = 234567890 where employee_id = 2;
1 row updated.
SQL>
SQL> update people set ssn = 345678901 where employee_id = 3;
1 row updated.
SQL>
SQL> alter table people
2 modify (
3 ssn number(9) not null
4 );
Table altered.
SQL>
SQL> desc people;
Name Null? Type
----------------------------------------------------------------------------------------------------------------- -------- ----------------------------------------------------------------------------
EMPLOYEE_ID NOT NULL NUMBER(9)
FIRST_NAME VARCHAR2(15)
LAST_NAME VARCHAR2(20)
EMAIL VARCHAR2(25)
SSN NOT NULL NUMBER(9)
SQL>
SQL> drop table people;
Table dropped.
SQL>
SQL>
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