You can identify exceptions to a specific integrity constraint while attempting to enable the constraint. All rows violating constraints are noted in an When a constraint is in the enable novalidate state, all subsequent statements are checked for conformity to the constraint.
statements, and identify the column or columns affected by the constraint and identify the conditions of the constraint.
If a constraint is disabled, then data that does not conform can be allowed to enter the database.Additionally, you can specify that existing data in the table must conform to the constraint ( To enforce the rules defined by integrity constraints, the constraints should always be enabled.If the constraint is in the enable novalidated state, violations resulting from data entered while the constraint was disabled remain.The rows that violate the constraint must be either updated or deleted in order for the constraint to be put in the validated state.However, while the constraint is disabled such a row can be inserted.
This row is known as an exception to the constraint.