Modifying Constraints¶

After a constraint is created:

• The constraint can be renamed.

• Some properties can be modified, e.g. RELY.

• Some properties cannot be modified, e.g. such as DEFERRABLE. To modify these properties, the constraint must be dropped and recreated.

• The column definition for a constraint cannot be modified, e.g. add new columns, drop existing columns, or change the order of columns. To make these types of changes, the constraint must be dropped and recreated.

When modifying a constraint, the constraint can be identified using either the constraint name or the columns in the constraint definition along with the type of the constraint. Primary keys can also be identified using the PRIMARY KEY keyword, because each table can have only a single primary key.

If a table with constraints is modified, e.g. rename table or swap table with another table, the constraints are updated to reflect the changes.

ALTER TABLE <table_name> RENAME CONSTRAINT <old_name> TO <new_name>;

ALTER TABLE <table_name>
    { ALTER | MODIFY } { CONSTRAINT <name> | PRIMARY KEY | { UNIQUE | FOREIGN KEY } (<column_name>, [ ... ] ) }
    { [ [ NOT ] ENFORCED ] [ VALIDATE | NOVALIDATE ] [ RELY | NORELY ] };