SYSCONSTRAINTS system table

Describes the information common to all types of constraints within the current database (currently, this includes primary key, unique, foreign key, and check constraints).
Column Name Type Length Nullable Contents
CONSTRAINTID CHAR 36 false unique identifier for constraint
TABLEID CHAR 36 false identifier for table (join with SYSTABLES.TABLEID)
CONSTRAINTNAME VARCHAR 128 false constraint name (internally generated if not specified by user)
TYPE CHAR 1 false P (primary key), U (unique), C (check), or F (foreign key)
SCHEMAID CHAR 36 false identifier for schema that the constraint belongs to (join with SYSSCHEMAS.SCHEMAID)
STATE CHAR 1 false E for enabled, D for disabled
REFERENCECOUNT INTEGER 1 false the count of the number of foreign key constraints that reference this constraint; this number can be greater than zero only for PRIMARY KEY and UNIQUE constraints