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Strong entity set and weak entity set?
Strong entity set and weak entity set: A strong entity set has a primary key. All tuples in the set are distinguishable through that key. A weak entity set has no primary key unless attributes of the strong entity set on that it depends are involved. Tuples in a weak entity set are partitioned according to their relationship along with tuples within a strong entity set. Tuples within each partition are distinguishable through a discriminator that is a set of attributes. A strong entity set has a primary key. All tuples in the set are distinguishable through that key. A weak entity set has no primary key unless attributes of the strong entity set on that it depends are included. Tuples in a weak entity set are partitioned according to their relationship along with tuples in a strong entity set. Tuples within every partition are distinguishable through a discriminator, which is a set of attributes.
Q. Explain the terms key constraints participation constraints and mapping caradinalities in ER model. Participation Constraints : The participation of an entity set E i
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With the help of an example display how records can be deleted and updated in QBE. (i) Increase Pay_Rate of employees along with the skill of ‘cook' by 10%. (ii) Delete employee
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