SQL ALTER TABLE syntax and example tutorial

SQL ALTER TABLE syntax and example tutorial

After the alter table statement allows you to change the structure of a TABLE, it is created. Address terms that can be added to a new column. Existing columns may be deleted from the Drop clause table.

The syntax of the alter table statement is as follows:

Alter table table_name
ADD column_name data_type

Alter table table_name
Drop column column_name
Note: The alter table statement is not in the ANSI/ISO standard. This means that all SQL statements implement different terms and command syntax in business dialects.

Example #1

Alter table Orders
ADD Quantity SMALLINT

In this example, add a column to the order table by specifying the name and Data Type of the new column.

Example #2
Alter table EmployeeAddressTable
ADD Description VARCHAR (20) DEFAULT 'usa' NOT NULL

In this example, a column named "Description" is added to the "EmployeeAddressTable" table. We also add a reserved word that is not NULL. valid data is required to be added to this column and a default value is specified.

Example #3

Alter table AntiqueOwners drop column State