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Define entity integrity and referential integrity. How does SQL allow specification of these?
Ans: Entity Integrity Rule- If the attribute A of relation R is a prime attribute of R after that A cannot accept null values.
Referential Integrity Rule- In referential integrity, it is made sure that a value that appears in one relation for a given set of attributes as well appears for a particular set of attributes in another relation.
In SQL, referential integrity and entity integrity rules are implemented as constraints on the relation known as reference Key constraint and primary Key constraint correspondingly.
These constraints can be fixed with relation at the time of creation of the relations or after the creation of the relations by altering the definition of the relations. For instance:
In E-R diagram how generalization is represented? in E-R diagram generalization is represented by Triangle shape.
Consider employee (e_no, e_name, e_salary, d_code), dept (d_code, d_name) and dependent (depndt_name, e_no, relation). Show the names of employees in purchase and accounts departm
Discuss the problem of Spurious tuples and how we may prevent it. Ans: A spurious tuple is, mainly, a record in a database that gets created while two tables are joined bad
Key to represent relationship amongs tables is called ? A Key that represent the relationship between tables is called Foreign Key.
Equi Join: A join in which the joining condition is based on equality among values in the common columns. Common columns show (redundantly) in the result table. Let us Consider th
Outer Join: The use of Outer Join is that it still joins those tuples that do not have matching values in common columns are also contained in the result table. Outer join places
Complete replication: It implies maintaining of a whole copy of the database at every site. Thus, the reliability & availability and performance for query response are maximized.
what is the relationship between receipt and owner entities in computer sales and service company
Differentiate between Key and superkey? Key and superkey - A key a single attribute or a combination of two or more attributes of an entity set in which is used to identify o
What are the two distinct aspects to the implementation of associations? i) It is required to define data declarations which will enable details of actual links to be stored. I
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