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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:
Candidate Key: In a relation R, a candidate key for R is a subset of the set of attributes of R, which have the differnt two properties: (1) Uniqueness: N
Explain forms based and graphical interface? Forms based and graphical interface: graphical user interface (GUI) is a kind of user interface which permits people to interact
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What is transaction? Transaction is a unit of program implementation that accesses and possibly updated several data items.
What is entity in DBMS? Entity: A DBMS entity is either a thing in the modelled world or a drawing element in an ERD.
explain the steps for reduction of er model into relational model?
Explain CNT in the respects of QBE ? CNT: It is one of the aggregation commands given in QBE. It is used to identify number of tuples
why three level architecture had been developed/
How does the system cope up with a record crash when recovery is going on after the first crash? Ans: In a system the undo and redo operations are needed to be idempotent to c
Our company hires independent contractors to install equipment at precise locations across North America. We want to track the installation data and generate reports. The compan
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