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!
Explain entity integrity and referential integrity rules within relational model. Show how these are realized in SQL?
Entity Integrity Rule - No primary key value could be null.
Referential Integrity Rule - In referential integrity, it is ensured in which a value which appears in one relation for a given set of attributes also appears for a certain set of attributes within another relation.
In SQL, entity integrity and referential integrity rules are implemented as constraints on the relation known as primary key constraint or reference key constraint corresponding. These constraints can be specified along with relation at the time of creation of the relations or after the creation of the relations through altering the definition of the relations. For instance:
CREATE TABLE DEPT
(DEPTNO NUMBER PRIMARY KEY,
DNAME VARCHAR2(15));
CREATE TABLE EMP
(EMPNO NUMBER PRIMARY KEY,
20
ENAME VARCHAR2(15),
JOB VARCHAR2(10),
DEPTNO NUMBER REFERENCES DEPT(DEPTNO));
i need help for assignment ..
Using Column aliases Example: To print column names as NAME and ANNUAL SALARY SELECT ENAME "NAME", SAL*12 "ANNUAL SALARY" FROM EMP;
#question benefits and limitations of data models..
what is definition hierarchical data model
SELECT Statement This statement is used for retrieving information from the databases. It can be coupled with many clauses. Let us talk about these clauses in more detail:
explain multi key file organisation
What is an object ID? Each class-derived table has an ID for primary key, one or more object IDs form primary key for association derived tables. An object ID is equivalent dat
What is database Trigger? A database trigger is a PL/SQL block that can explained to automatically execute for insert, update, and delete statements against a table. The trigge
Entity types that do not have any key attribute, and therefore cannot be identified independently, are known as weak entity types. A weak entity can be recognized uniquely only by
Give Concurrent sub states diagram for the classroom and exam held. In Figure, simultaneous substrates have been taken. After passing Minor 1 test you could give Minor 2 test. T
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