The USER_CONSTRAINTS view provides information about all constraints placed on tables that are owned by the current user.

ownerTEXTThe name of the owner of the constraint.
schema_nameTEXTName of the schema in which the constraint belongs.
constraint_nameTEXTThe name of the constraint.
constraint_typeTEXTThe constraint type. Possible values are: C – check constraint; F – foreign key constraint; P – primary key constraint; U – unique key constraint; R – referential integrity constraint; V – constraint on a view; O – with read-only, on a view
table_nameTEXTName of the table to which the constraint belongs.
search_conditionTEXTSearch condition that applies to a check constraint.
r_ownerTEXTOwner of a table referenced by a referential constraint.
r_constraint_nameTEXTName of the constraint definition for a referenced table.
delete_ruleTEXTThe delete rule for a referential constraint. Possible values are: C – cascade; R - restrict; N – no action
deferrableBOOLEANSpecified if the constraint is deferrable (T or F).
deferredBOOLEANSpecifies if the constraint has been deferred (T or F).
index_ownerTEXTUser name of the index owner.
index_nameTEXTThe name of the index.
constraint_defTEXTThe definition of the constraint.