DROP

DROP COLUMN

The DROP COLUMN command removes a column from an existing table.

The provided SQL statement deletes the “ContactName” column from the “Customers” table.

Example

ALTER TABLE Customers DROP COLUMN ContactName;

DROP a UNIQUE Constraint

To remove a UNIQUE constraint, employ the following SQL statement:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons DROP CONSTRAINT UC_Person;

MySQL:

ALTER TABLE Persons DROP INDEX UC_Person;

DROP a PRIMARY KEY Constraint

To remove a PRIMARY KEY constraint, execute the following SQL statement:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons DROP CONSTRAINT PK_Person;

MySQL:

ALTER TABLE Persons DROP PRIMARY KEY;

DROP a FOREIGN KEY Constraint

To eliminate a FOREIGN KEY constraint, utilize the following SQL statement:

SQL Server / Oracle / MS Access:

ALTER TABLE Orders DROP CONSTRAINT FK_PersonOrder;

MySQL:

ALTER TABLE Orders DROP FOREIGN KEY FK_PersonOrder;

DROP a CHECK Constraint

To remove a CHECK constraint, execute the following SQL statement:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons DROP CONSTRAINT CHK_PersonAge;

MySQL:

ALTER TABLE Persons DROP CHECK CHK_PersonAge;

DROP DEFAULT

The DROP DEFAULT command removes a DEFAULT constraint.

To eliminate a DEFAULT constraint, execute the following SQL statement:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons ALTER COLUMN City DROP DEFAULT;

MySQL:

ALTER TABLE Persons ALTER City DROP DEFAULT;

DROP INDEX

The DROP INDEX command is employed to remove an index from a table.

MS Access:

DROP INDEX index_name ON table_name;

SQL Server:

DROP INDEX table_name.index_name;

DB2/Oracle:

DROP INDEX index_name;

MySQL:

ALTER TABLE table_name DROP INDEX index_name;

DROP DATABASE

The DROP DATABASE command is used to delete an existing SQL database.

The provided SQL drops a database named “testDB”.

Example

DROP DATABASE testDB;

Caution: Exercise caution before dropping a database. Deleting a database will lead to the loss of all information stored within it!

DROP TABLE

The DROP TABLE command eliminates a table from the database.

The subsequent SQL statement removes the “Shippers” table:

Example

DROP TABLE Shippers;

Caution: Exercise care prior to deleting a table. Deleting a table leads to the loss of all data stored within it!

DROP VIEW

The DROP VIEW command removes a view.

The following SQL drops the “Brazil Customers” view:

Example

DROP VIEW [Brazil Customers];