What are the several kinds of the update operations on relations? Also explain the constraints on these update operation. Give instance in support of your answer.
There are three primary update separation on relations:
(i) Insert : It is used to insert a latest tuple or tuples in a relation. Insert can violate any of the four tuples of constraints: Domain constraints, key constraints, entity integrity and referential integrity
(ii) Delete : It is used to delete tuples. The delete operation can violate just referential integrity, if the tuple being deleted is referenced through the foreign keys from other tuples in the database
(iii) Modify: It is used to change value of a few attributes in existing tuples. Modify can also violate any of the four constraints as specified within insert operation.
Examples:
(1) Inserting a tuple having null value for primary key violates entity integrity
(2) Deleting a tuple in a table for that tuples exist other tables that are dependent on those tuples will violate referential key integrity.
(3) Modifying a primary key attribute to any other such that is aheady exists in the table will violate entity integrity.