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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.
Unrepeatable reads : Assume T7 reads X twice during its implementation. If it did not update X itself it could be very disturbing to see a dissimilar value of X in its next read. B
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Consider the following frequency counts of some itemsets in a transaction database r : freq({A}, r) = 0.405 freq({B}, r) = 0.510 freq({C}, r) = 0.303 freq({A
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Consider the entity type dependent related to employee entity, which is used to keep track of the dependents of every employee. The attributes of dependents are: name, sex, birth d
give some example real-life situations where DBMS are most suiitabe
Determine the language that needs a user to specify the data to be retrieved with no specifying exactly how to get it is Ans: Non-Procedural DML
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