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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.
A collection of a same kind of entities is known as an Entity Set or entity type. Example: For the COLLEGE database defines earlier objects of concern are Students, Faculty,
Gyan Gurukul is a software company that provides software related solution. Ashutosh Dubey who is the director of Gyan Gurukul want a three-level schema architecture for the Gyan G
Improved Reliability: In a centralised DBMS, a server failure stops the operations of the DBMS. Though, a failure at single site of a DDBMS, or a failure of a communication link cr
Create an index for the table Client, field CLIENT_NO of Q ? Command: CREATE INDEX client_client_no ON client(client_no);
Hot Backup: Some sites cannot terminate the database while creating a backup copy of the files. The cold backup is not a reliable option. So different kinds of backing up database
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how does Btree differ from a B+ - tree?
Domain Constraints Domain constraints are primarily formed for defining the logically correct values for an attribute of a relation. The relation allows attributes of a relatio
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