SQL DROP Keyword

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DROP COLUMN

The DROP COLUMN command is used to delete a column in an existing table.

The following SQL deletes the "ContactName" column from the "Customers" table:

Example

ALTER TABLE Customers
DROP COLUMN ContactName;

DROP a UNIQUE Constraint

To drop a UNIQUE constraint, use the following SQL:

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 drop a PRIMARY KEY constraint, use the following SQL:

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 drop a FOREIGN KEY constraint, use the following SQL:

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 drop a CHECK constraint, use the following SQL:

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 is used to delete a DEFAULT constraint.

To drop a DEFAULT constraint, use the following SQL:

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 used to delete an index in 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 is to delete an existing SQL database.

The following SQL drops a database named "testDB":

Example

DROP DATABASE testDB;

Note: Be careful before dropping a database. Deleting a database will result in loss of complete information stored in the database!

DROP TABLE

The DROP TABLE command deletes a table in the database.

The following SQL deletes the table "Shippers":

Example

DROP TABLE Shippers;

Note: Be careful before deleting a table. Deleting a table results in loss of all information stored in the table!

DROP VIEW

The DROP VIEW command deletes a view.

The following SQL drops the "Brazil Customers" view:

Example

DROP VIEW [Brazil Customers];

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