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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:
as a customer service employee, explain five measures you would recommend a displeased student to patronise a school canteen
what is relationship inheritance and attribute inheritance
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What are domain constraints? A domain is a set of values that might be assigned to an attribute .all values that appear in a column of a relation must be taken from the similar
Need for Multiple Access Paths In practice, most of the online information systems need the support of multi-key files. For example, consider a banking database application hav
Benefits: It limits data access. It makes difficult queries look easy. It permits data independence. It presents dissimilar views of the similar data.
What is the difference among a database schema and a database state? The collection of information stored in database at particular moment in time is known as database state a
Write an sql statement to find what is the percentage of home policies which are from the state of Arizona out of all Home policies by Policy Value.
Chapter 10a review questions
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