Appendix D. System Tables - D.30 RDB$RELATION_CONSTRAINTS - 《Firebird 4.0 Language Reference》

D.30 `RDB$RELATION_CONSTRAINTS`

RDB$RELATION_CONSTRAINTS stores the definitions of all table-level constraints: primary, unique, foreign key, CHECK, NOT NULL constraints.

Column Name	Data Type	Description
`RDB$CONSTRAINT_NAME`	`CHAR(63)`	The name of the table-level constraint defined by the user, or otherwise automatically generated by the system
`RDB$CONSTRAINT_TYPE`	`CHAR(11)`	The name of the constraint type: `PRIMARY KEY`, `UNIQUE`, `FOREIGN KEY`, `CHECK` or `NOT NULL`
`RDB$RELATION_NAME`	`CHAR(63)`	The name of the table this constraint applies to
`RDB$DEFERRABLE`	`CHAR(3)`	Currently `NO` in all cases: Firebird does not yet support deferrable constraints
`RDB$INITIALLY_DEFERRED`	`CHAR(3)`	Currently `NO` in all cases
`RDB$INDEX_NAME`	`CHAR(63)`	The name of the index that supports this constraint. For a `CHECK` or a `NOT NULL` constraint, it is `NULL`.