New added columns are empty : Alter Table « Table « Oracle PL/SQL Tutorial

SQL> create table employee(
  2    employee_id     number(9),
  3    first_name      varchar2(15),
  4    last_name       varchar2(20),
  5    email           varchar2(25),
  6    constraint pk_employee primary key (employee_id)
  7  );

Table created.

SQL>
SQL> insert into employee
  2  values (1, 'Tom', 'Kyte', 't@aaa.com');

1 row created.

SQL>
SQL> insert into employee
  2  values (2, 'Sean', 'Dillon', 's@aaa.com');

1 row created.

SQL>
SQL> insert into employee
  2  values (3, 'Christopher', 'Beck', 'c@aaa.com');

1 row created.

SQL>
SQL> commit;

Commit complete.

SQL>
SQL> select *
  2  from employee;


EMPLOYEE_ID FIRST_NAME           LAST_NAME            EMAIL
----------- -------------------- -------------------- -------------------------
          1 Tom                  Kyte                 t@aaa.com
          2 Sean                 Dillon               s@aaa.com
          3 Christopher          Beck                 c@aaa.com

3 rows selected.

SQL> alter table employee
  2  add (
  3    phone_number    varchar2(10)
  4  )
  5  /

Table altered.

SQL>
SQL> select *
  2  from employee;


EMPLOYEE_ID FIRST_NAME           LAST_NAME            EMAIL                     PHONE_NUMB
----------- -------------------- -------------------- ------------------------- ----------
          1 Tom                  Kyte                 t@aaa.com
          2 Sean                 Dillon               s@aaa.com
          3 Christopher          Beck                 c@aaa.com

3 rows selected.

SQL> drop table employee;

Table dropped.

SQL>
SQL>

6.3.Alter Table
	6.3.1.	Altering a Table
	6.3.2.	Some of the aspects of a column you can modify using ALTER TABLE
	6.3.3.	Adding a Column
	6.3.4.	ADD initially_created DATE DEFAULT SYSDATE NOT NULL;
	6.3.5.	Changing the Size of a Column
	6.3.6.	Decrease the length of a column
	6.3.7.	Changing the Precision of a Numeric Column
	6.3.8.	Decrease the precision of a numeric column
	6.3.9.	Changing the Data Type of a Column
	6.3.10.	Fill data into new added table column
	6.3.11.	Changing the Default Value of a Column
	6.3.12.	Alter table to add new constraint for new added column
	6.3.13.	ALTER TABLE to DISABLE a CONSTRAINT
	6.3.14.	Alter table to add primary key
	6.3.15.	Alter table to add primary key across more than one columns
	6.3.16.	Dropping a Column
	6.3.17.	New added columns are empty
	6.3.18.	Alter table to add unique with tablespace and storage setting
	6.3.19.	Alter table to add primary key with tablespace and storage setting
	6.3.20.	alter table nologging