ALTER TABLE

The SQL ALTER TABLE statement is used to add, modify, or drop columns in a table.

The general format is:

ALTER TABLE [schema.]tablename {ADD|MODIFY|DROP}...

Example 1, rename a table:

ALTER TABLE tablename RENAME TO newtablename;

Example 2, add column:

ALTER TABLE invoice ADD detailname varchar2(50);

Example 3, modify column:

ALTER TABLE invoice MODIFY detailname varchar2(50);
ALTER TABLE invoice MODIFY detailname NOT NULL;

Example 4, drop column:

ALTER TABLE invoice DROP COLUMN detailname;

Example 5, rename column:

ALTER TABLE invoice RENAME COLUMN detailname TO longname;

Example 6, default value:

ALTER TABLE invoice MODIFY detailname Varchar2(135) DEFAULT 'ABC...';

Example 7, add multiple columns:

ALTER TABLE invoice ADD (detailname varchar2(50), numitems number(6));