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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));
Explain trigger? Trigger: A database trigger is procedural code which is automatically executed within response to certain events on a particular table in a database. Trigger
Briefly describe concurrency execution? Lock - based protocols Locks There are several modes in which a data item may be locked in this section we restrict our attention
what is attribute is attribute inheritance in dbms?
Describe how you can simplify Operations. To simplify operation, one should use inheritance, where possible to use, to reduce the quantity of distinct operations. Introduce new
Primary index A primary index is a file that has a sorted series of records having two columns: a block address for that key field in the data file; and the ordering key field.
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What is a candidate key? Minimal super keys are known as candidate keys.
Question 1: Define the term business intelligence tools? Briefly explain how the data from one end gets transformed into information at the other end? Definition Exp
Aggregate functions Some of these functions are min, count, max, and avg. These functions help in getting consolidated information from a set of tuples. Example:
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