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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:
domain
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what is completeness constrent?
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Explain weak and strong entity sets? Weak and Strong entity sets: A physically powerful entity set has a primary key. All tuples in the group are distinguishable through that k
various techniques of hashing?
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Differentiate between a unique key and a primary key. - By default, clustered index on column are created by primary key while nonclustered index are created by unique key.
Forward Recovery (Redo): In this system the committed changes made by a transaction are reapplied to a previous copy of the database. In simpler
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