4D Doc Center : ALTER TABLE

4D v12.1

ALTER TABLE



	ALTER TABLE sql_name {ADD column_definition [PRIMARY KEY]\| DROP sql_name \| ADD primary_key_definition \| DROP PRIMARY KEY \| ADD foreign_key_definition \| DROP CONSTRAINT sql_name \| [{ENABLE \| DISABLE} REPLICATE] \| SET SCHEMA sql_name}

Description

The ALTER TABLE command is used to modify an existing table (sql_name). You can carry out one of the following actions:
Passing ADD column_definition adds a column to the table. The PRIMARY KEY keyword is used to set the primary key when a column is added.
Passing DROP sql_name removes the column named sql_name from the table.
Passing ADD primary_key_definition adds a PRIMARY KEY to the table.
Passing DROP PRIMARY KEY removes the PRIMARY KEY of the table.
Passing ADD foreign_key_definition adds a FOREIGN KEY to the table.
Passing DROP CONSTRAINT sql_name removes the specified constraint from the table.
Passing ENABLE REPLICATE or DISABLE REPLICATE enables or disables the mechanism allowing replication of the table (see the section).
Passing SET SCHEMA sql_name transfers the table to the sql_name schema.

Example

This example creates a table, inserts a set of values into it, then adds a Phone_Number column, adds another set of values and then removes the ID column:

CREATE TABLE ACTOR_FANS
(ID INT32, Name VARCHAR);

INSERT INTO ACTOR_FANS
(ID, Name)
VALUES(1, 'Francis');

ALTER TABLE ACTOR_FANS
ADD Phone_Number VARCHAR;

INSERT INTO ACTOR_FANS
(ID, Name, Phone_Number)
VALUES (2, 'Florence', '01446677888');

ALTER TABLE ACTOR_FANS
DROP ID;