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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:
What Is Recovery? During the life of a transaction, i.e., a after the start of a transaction but before the transaction commits, various changes may be made in a database state
What is meant by computing the closure of a set of functional dependency? The closure of F denoted by F + is the set of functional dependencies logically implied by F.
What are the ways of obtaining the connection parameters? Hardwire the parameters into the program. Ask for the parameters interactively. Get the parameters
Although how will the system recover The selection of REDO or UNDO for a transaction for the recovery is completed on the basis of the state of the transactions. This state is
Design Of Distributed Databases: The distributed databases are mainly relational at local level. So a local database schema is the similar as that of a centralised database design
Drawbacks of Database systems ?
By which techniquesTransaction processing is associated? Transaction processing is associated by producing detail, summary, or exception reports and recording a business activi
What is multiple relationship ?
Give the reasons for allowing concurrency? The reasons for allowing concurrency is if the transactions run serially, a short transaction might have to wait for a preceding long
What are the various forms of data transparency? a) fragmentation transparency b) replication transparency c) location transparency
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