Oracle Alter Statement


To add, delete, or modify columns in an existing table. The ALTER TABLE statement is used.

Oracle ALTER TABLE Syntax

To add a column in a table, the syntax is

ALTER TABLE table_name
ADD column_name column-datatype;

How to add multiple columns in the existing table

syntax:

ALTER TABLE table_name
ADD (column_1 column-datatype,
column_2 column-datatype,
...
column_n column_datatype);

Example:

ALTER TABLE students
ADD (student_type varchar2(40),
student_address varchar2(40));

How to modify column of a table

syntax:

ALTER TABLE table_name
MODIFY column_name column_type;

Example:

ALTER TABLE students
MODIFY student_name varchar(200) not null;

How to modify multiple columns of a table

syntax:

ALTER TABLE table_name
MODIFY (column_1 column_type,
column_2 column_type,
...
column_n column_type);

Example:

ALTER TABLE students
MODIFY (student_name varchar(200) not null,
class varchar(200));

How to rename column of a table

syntax:

ALTER TABLE table_name
RENAME COLUMN old_name to new_name;

Example:

ALTER TABLE students
RENAME COLUMN student_name to lname;







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