The DBA_CONS_COLUMNS view provides information about all columns that are included in constraints that are specified in on all tables in the database.

ownerTEXTUser name of the constraint’s owner.
schema_nameTEXTName of the schema in which the constraint belongs.
constraint_nameTEXTThe name of the constraint.
table_nameTEXTThe name of the table to which the constraint belongs.
column_nameTEXTThe name of the column referenced in the constraint.
positionSMALLINTThe position of the column within the object definition.
constraint_defTEXTThe definition of the constraint.