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Describes the several relationship constraints through giving suitable example?
Constraints on relationships: There are two kinds of constraints on relationships.
1) Mapping cardinalities or cardinality ratios express the number of entities to that another entity can be associated through a relationship set. For a binary relationship set among entities A and B. The mapping cardinality may be any one of the subsequent:
a) One to One: An entity in A is related along with at most one entity in B and an entity in B is related with at most one entity in A.b) One to Many: An entity in A can be related with any number in B but an entity in B is associated with at most one in A.c) Many to one: An entity in A is related with at most one in B but an entity in B is associated with any number in A.d) Many to Many: An entity in A and B can be associated along with any number of entities in the other entity set.
2) Participation constraints: The participation of an entity set E in a relationship set R is said to be total if every entity in E participates within at least one relationship in R. If only a few entities in E participation of entity set E in relationship R is said to be partial.
Primary index A primary index is a file that has a sorted series of records having two columns: a block address for that key field in the data file; and the ordering key field.
These permit the user to unload a database or parts of a database and reload the data on the similar machine, or on another machine in a dissimilar location. This can be useful in
CREATE TABLE prodtrans ( pno number (4) ptype char (1) CHECK (ptype in ('I','R','S')), qty number (5) FOREIGN KEY pno REFERENCES product (pno) ON DELETE CASCADE);
explain in detail about time stamp orderting/
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What are the various symbols used to draw an E-R diagram (any 3)?
The following variant of the primary copy asynchronous-update replication protocol has been proposed for totally replicated systems. (a) A transaction executing at site A updat
What is Derived and stored Attribute? Derived and Stored Attribute - In a few cases, two or more attribute values are associated, for example, Age and BirthDate attributes of a
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A student entity type has the following attributes,name..
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