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];