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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 are the kinds of Strings? -A binary string in MySQL is one that MySQL treats as case sensitive in comparisons. -A non binary string in MySQL is one that MySQL does'nt
3NF Normal Form A relation schema R is in 3NF if it is in 2NF and for each FD X A either of the following is true X is a Super-key of R. A is a prime attribute of R
Do the 11.1 11.1 Credit Card Use. Consider the following hypothetical bank data on consumers’ use of credit card credit facilities in Table 11.3. Create a small worksheet in Exce
What is a PROJECT operation? The project operation is a unary operation that returns its argument relation with particular attributes left out. Projection is shown by pie (π).
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