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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 the use of rename operation? Rename operation is used to rename both relations and an attributes. It uses the as clause, taking the form: Old-name as new-name.
System error :These contain errors in database system or the OS, example, deadlocks.Such errors are fairly hard to detect and need reprogramming the erroneous components of the sys
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Functional Dependency Consider a relation R that has 2 attributes A and B. The attribute B of the relation is functionally dependent on the attribute A if and only if for every
Explain I command in QBE ? I : It is the command in QBE that is used to insert tuple (s) into the database
can you create a database for me in oracle/sql
What are the advantages of having an index structure? Ans: The index structures commonly provide secondary access paths, which offer alternative ways of accessing the reco
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Design an algorithm to implement operations Each and every operation specified in the functional model could be formulated as an algorithm. The algorithm indicates how operat
Define weak and strong entity sets? Weak entity set: entity set that do not have key attribute of their own are known as weak entity sets. Strong entity set: Entity set that
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