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

ownerTEXTName of the owner of the constraint.
schema_nameTEXTName of the schema in which the constraint belongs.
constraint_nameTEXTName 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 was deferred (T or F).
index_ownerTEXTUser name of the index owner.
index_nameTEXTName of the index.
constraint_defTEXTDefinition of the constraint.