The DROP keyword is used to delete existing columns, constraints, databases, indexes, tables, and views.

The following deletes a database called “sitename_db”.

DROP DATABASE sitename_db;

The following deletes the table Customers.

DROP TABLE Customers;

The following deletes the county secondary_email column from the Customers table.

ALTER TABLE Customers
DROP COLUMN secondary_email;

The following deletes the unique constraint named uc_customer_names from the Customers table.

MySQL:

ALTER TABLE Customers
DROP INDEX uc_customer_names;

SQL Server:

ALTER TABLE Customers
DROP CONSTRAINT uc_customer_names;

The following deletes the primary key constraint named pk_customer_names from the Customers table.

MySQL:

ALTER TABLE Customers
DROP PRIMARY KEY;

SQL Server:

ALTER TABLE Customers
DROP CONSTRAINT pk_customer_names;

The following deletes the foreign key constraint named fk_customer_names from the Customers table.

MySQL:

ALTER TABLE Customers
DROP FOREIGN KEY fk_customer_names;

SQL Server:

ALTER TABLE Customers
DROP CONSTRAINT fk_customer_names;

The following deletes the check constraint named chk_age from the Persons table.

MySQL:

ALTER TABLE Persons
DROP CHECK chk_age;

SQL Server:

ALTER TABLE Persons
DROP CONSTRAINT chk_age;

The following deletes the default country value requirement from the Customers table.

MySQL:

ALTER TABLE Customers
ALTER country DROP DEFAULT;

SQL Server:

ALTER TABLE Customers
ALTER COLUMN country DROP DEFAULT;

The following deletes an index named “idx_customer” from the Customers table.

MySQL:

ALTER TABLE Customers
DROP INDEX idx_customer;

SQL Server:

DROP INDEX Customers.idx_customer;

The following drops a view called “Canada Customers”.

DROP VIEW [Canadian Customers]';

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