Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
During the deletion of a tuple two cases can happen:
Deletion of tuple in relation having the foreign key: In this type of case simply delete the desired tuple. For example, in ASSIGNMENT relation we can simply delete the first tuple.
Deletion of the target of a foreign key reference: For instance, an attempt to delete an employee tuple in EMPLOYEE relation whose EMPID is 101. This employee shown not only in the EMPLOYEE but also in the ASSIGNMENT relation. Can these tuple be deleted? If we delete the tuple in EMPLOYEE relation then two unequalled tuples are left in the ASSIGNMENT relation, therefore causing violation of referential integrity constraint. Therefore, the following two choices be for such deletion:
RESTRICT - The delete operation is "restricted" to only the situation where there are no such matching tuples. For instance, we can delete the EMPLOYEE record of EMPID 103 as there is no matching tuple in ASSIGNMENT but not the record of EMPID 101.
CASCADE - The delete operation "cascades" to delete also those matching tuple. For instance, if the delete mode is CASCADE then deleting employee having
EMPID as 101 from EMPLOYEE relation will also make deletion of 2 more tuples from ASSIGNMENT relation.
What is Relational DBMS This is our subject of study. A DBMS is relational if the data is organized into relations, that is, tables. In RDBMS, all data are kept in the well-kno
What Is Recovery? During the life of a transaction, i.e., a after the start of a transaction but before the transaction commits, various changes may be made in a database state
Ancestry database records information about family trees . Following information is recorded about each person: FIRSTNAME first name SURNAME surname MNAME maiden name (if
What is the use of unique function? UNIQUE function: If UNIQUE is specified then only unique values are used to computed the mean.
Define the basic operations of the relational algebra? Ans: Basic operators of relational algebra are: 1. Union (∪) - Selects tuples which are in either P or Q or in bot
Differance between procedural and non procedural DML? Procedural and non procedural DML Procedural DML exactly what data is require and how to obtain those data. Non procedural
What is E-R model? This data model is based on real world that having of basic objects called entities and of relationship between these objects. Entities are explained in a da
Meaningful use refers to the use of certified EHR technology to "enhance quality, efficiency, and reduce health disparities
Which two files are used during operation of the DBMS? Data dictionary and transaction log are two files used during operation of the DBMS.
Define union compatibility? Explain why INTERSECTION of two relations cannot be performed if they are not union compatible? Two relations R(A1, A2,-------, An) and S(B1, B2,--
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd