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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));
er diagram on cosmetics.
File Organisation And Its Types Just as arrays, trees, lists and other data structures are used to execute data Organisation in main memory, a number of planning's are used to
Example : Search the name, department number and salary of employees drawing minimum salary in that department. SELECT ENAME, SAL, DEPTNO FROM EMP WHERE SAL IN (SELECT MI
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Gaps in sequence values can happen when: - A rollback happens that is when a statement changes are not accepted. - When the system crashes - When a sequence i
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Distributed And Client Server Databases Introduction This unit tells the distributed database systems which are primarily relational and one important execution model: the
Describe the static hash file with buckets and chaining and show how insertion, deletion and modification of a record can be performed. In static hash file organization, the wo
Project Description: I need a point of sale for motels. It needs to run on windows and requires being network able so that we can have more than one computer using it at once.
What are called index-sequential files? The files that are ordered sequentially with a primary index on the search key are known as index-sequential files
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