SYS_REFERENTIAL_CONSTRAINTS

SYS_REFERENTIAL_CONSTRAINTS contains information about foreign key relationships between tables.

Column name	Data type	Description
`CONSTRAINT_CATALOG`	`VARCHAR(128)`	A top-level container for constraints. Not used. Always `NULL`.
`CONSTRAINT_SCHEMA`	`VARCHAR(128)`	A second-level container for constraints. Not used. Always `NULL`.
`CONSTRAINT_NAME`	`VARCHAR(128)`	The name of the foreign key constraint.
`UNIQUE_CONSTRAINT_CATALOG`	`VARCHAR(128)`	A top-level container for referenced constraints. Not used. Always `NULL`.
`UNIQUE_CONSTRAINT_SCHEMA`	`VARCHAR(128)`	A second-level container for referenced constraints. Not used. Always `NULL`.
`UNIQUE_CONSTRAINT_NAME`	`VARCHAR(128)`	The name of the referenced constraint.
`MATCH_OPTION`	`VARCHAR(7)`	Not used. Always `NONE`.
`UPDATE_RULE`	`VARCHAR(9)`	Not used. Always `NO ACTION`.
`DELETE_RULE`	`VARCHAR(9)`	An action to perform when a SQL statement violates this referential constraint. The possible values are: `NO ACTION` – The `DELETE` on the referenced primary key does not affect the foreign key. `CASCADE` – The `DELETE` on the referenced primary key causes cascading deletes of all related records.
`OBJECT`	`VARCHAR(128)`	The name of the table to which this foreign key belongs.
`FIELD`	`VARCHAR(128)`	The foreign key column.
`RELATED_OBJECT`	`VARCHAR(128)`	The name of the table referenced by the foreign key.
`RELATED_FIELD`	`VARCHAR(128)`	The name of the field referenced by the foreign key. Always `ID`.