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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:
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Question: Consider the following database relations for a textbook ordering system used by a college bookshop: Book (b-copy#, bname, ISBN#, author, price, subject) Order (s#
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A field-groups statement or an insert statement reverses storage space and transfers values. False.
What is a value? A data value is used for identity. This form of identity is used in relational systems.eg: The primary key value of a tuple recognize the tuple.
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These are the binary operations; i.e., each is applied to two relations or sets. These two relations can be union compatible excluding in case of Cartesian product. Two relations R
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