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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));
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
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What is an index? An index is a structure that helps to place desired records of a relation quickly, without probing all records.
Explain differance between Primary and secondary storage ? Primary and secondary storage Computer storage is classified within primary(main) memory and secondary(per
Class Diagram A class diagram is required to support functional necessity of system. In a static design view, class diagram is used to model vocabulary of the system, simple c
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What is a primary key? Primary key is chosen by the database designer as the principal means of identifying an entity in the entity set.
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
Mention the purpose of SID and SOD lines SID (Serial input data line): It is an input line by which the microprocessor accepts serial data. SOD (Serial output data line)
Package classes and associations into models Programs are made of separate physical units which could be edited, imported, complied or otherwise manipulated. The careful part
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