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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));
Differance between Unordered and ordered file ? Unordered file do no has any sequence although ordered file has arranged in a few sequence and data are assigned in ordered form
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Project: Microsoft Access You have been asked by the ABC Tanning Salon to create a database that can be used to track the salon's customers. You are to create a table in Access
What are the different strategies of implementation of the Statecharts? There are two strategies for implementation of state charts: i) Basic Implementation Strategy
Explain CNT in the respects of QBE ? CNT: It is one of the aggregation commands given in QBE. It is used to identify number of tuples
What is meant by the degree of relationship set? The degree of relationship type is the number of participating entity types.
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write a short note on participation role? Participation role: roles are indicating in E-R diagram by labelling the lines that connect diamonds to rectangles.
What is persistency? Persistency ensures which data is stored and that after the object is no longer available (program stops running) the data will be available to other users
Advantages of Data Distribution The primary benefit of distributed database systems is the ability to access and share data in a reliable and efficient manner.
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