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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));
Relationship between Security and Integrity: Database security usually refers to access, while database integrity refers to avoidance of accidental loss of consistency. But usually
how to data store?
What is known as clustering file organization? In the clustering file organization, records of several dissimilar relations are stored in the similar file.
What is a Data Flow Diagram? Data Flow Diagram: A data flow diagram is the graph that shows flow of data values from their sources in objects in the course of processes whic
ER diagram on cosmetics
for the following business rules . Identify all entities, attributes, relationships, primary keys, cardinalities and constraints where appropriate 3. (9) An art museum owns a larg
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What are the disadvantages of relational approach? Disadvantages of relational approach: • Substantial hardware and system software overhead • May not fit all business models •
Define Direct file organization? The direct file organization is employed to enhance the performance in accessing the records than sequential file organization. In direct file
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