Modify Table Structure

Oracle basic syntax to modify table structure

Syntax 1
add a column into existing table

ALTER TABLE table_name
ADD column_name datatype;

example :
ALTER TABLE customer
ADD phone_number varchar(20);


Syntax 2
modify a data type of a field of existing table

ALTER TABLE table_name
MODIFY (column_name datatype);

example :
ALTER TABLE customer
MODIFY (name varchar(100));

create new table

Syntax 1

creating new table
----------------------------
CREATE TABLE table_name (
field1 datatype,
field2 datatype,
...);

example :
CREATE TABLE customer (
id number,
name varchar2(50));


Syntax 2
creating table from other existing table,
the structure of new table copied from source table.
----------------------------
CREATE TABLE table_name as select * from existing_table;

example :
CREATE TABLE customer2 as select * from customer;