NOVALIDATE

When you create a foreign key constraint in Oracle, the database ensures that the values in the foreign key column match the values in the referenced primary key column. However, there are situations where you might want to create a foreign key constraint without immediately validating existing data.

NOVALIDATE Behavior

  1. ENABLE VALIDATE
  2. ENABLE NOVALIDATE

 

 

ENABLE VALIDATE: This is the default behavior. When you create a foreign key constraint with this option, Oracle checks the existing data to ensure that it meets the referential integrity constraints. If the data violates the constraints, the constraint creation will fail.

 

ALTER TABLE child_table
ADD CONSTRAINT fk_constraint
FOREIGN KEY (column_name)
REFERENCES parent_table (column_name)
ENABLE VALIDATE;

 

ENABLE NOVALIDATE: This option allows you to create a foreign key constraint without checking the existing data. The constraint is still in effect for new data, but existing data is not immediately validated. This can be useful when you have existing data that violates the constraint, and you plan to clean it up later.

 

ALTER TABLE child_table
ADD CONSTRAINT fk_constraint
FOREIGN KEY (column_name)
REFERENCES parent_table (column_name)
ENABLE NOVALIDATE;

 

Important:

It’s important to note that using “ENABLE NOVALIDATE” can lead to a situation where the constraint is violated by existing data. You should only use this option if you have a plan to address any data inconsistencies and ensure that the constraint is eventually satisfied

 

 

 

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