# SYSFOREIGNKEYS system table

Describes the information specific to foreign key constraints in the current database.

Derby generates a backing index for each foreign key constraint; the name of this index is the same as SYSFOREIGNKEYS.CONGLOMERATEID.

Column Name | Type | Length | Nullability | Contents
--- | --- | --- | --- | ---
CONSTRAINTID | CHAR | 36 | false | unique identifier for the foreign key constraint (join with SYSCONSTRAINTS. CONSTRAINTID)
CONGLOMERATEID | CHAR | 36 | false | unique identifier for index backing up the foreign key constraint (join with SYSCONGLOMERATES. CONGLOMERATEID)
KEYCONSTRAINTID | CHAR | 36 | false | unique identifier for the primary key or unique constraint referenced by this foreign key (SYSKEYS.CONSTRAINTID or SYSCONSTRAINTS. CONSTRAINTID)
DELETERULE | CHAR | 1 | false | R for NO ACTION (default), S for RESTRICT, C for CASCADE, U for SET NULL
UPDATERULE | CHAR | 1 | false | R for NO ACTION(default), S for restrict

Parent topic: Derby system tables