ADD CONSTRAINT Clause

Description

You can add a new constraint by using the ADD CONSTRAINT clause.

By default, the index created when you add PRIMARY KEY constraints is created in ascending order, and you can define the key sorting order by specifying the ASC or DESC keyword next to the column name.

Syntax

ALTER [ TABLE | CLASS | VCLASS | VIEW ] table_name

ADD CONSTRAINT < constraint_name > column_constraint ( column_name_comma_list )

 

column_constraint ::=

UNIQUE [ KEY ] |

PRIMARY KEY |

FOREIGN KEY [ <foreign_key_name> ] REFERENCES [referenced_table_name]( column_name_comma_list )

                       [ <referential_triggered_action> ... ]

 

<referential_triggered_action> ::=

{ ON UPDATE <referential_action> } |

{ ON DELETE <referential_action> } |

{ ON CACHE OBJECT cache_object_column_name }

 

<referential_action> ::=

CASCADE | RESTRICT | NO ACTION | SET NULL

Example

ALTER TABLE a_tbl ADD CONSTRAINT PRIMARY KEY(id); 

ALTER TABLE a_tbl ADD CONSTRAINT PRIMARY KEY(id, no DESC);

ALTER TABLE a_tbl ADD CONSTRAINT UNIQUE u_key1(id);