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Attributes having a one value for a particular entity.
For instance, Age is a single valued attribute of a student entity.
Attributes that have more than single values for a specific entity is known as a multivalued attribute. Different entities may have dissimilar number of values for these types of attributes. For multivalued attributes we can also states the minimum and maximum number of vales that can be attached. For instance, phone number for a person entity is a multivalued attribute.
How does a query tree represent a relational algebra expression? Discuss any three rules for query optimisation, giving example as to when should each rule be applied. Ans
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