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Describe entity referential integrity and integrity. Give an example of each.
Entity Integrity Rule - If there is a attribute A of relation R is a prime attribute of R then A cannot accept null values.
Referential Integrity Rule - In referential integrity, it is ensured in which a value in which appears in one association for a given set of attributes also appears for a certain set of attributes in another relation.
For example:
Roll No is the primary key within the relation STUDENT and Roll No + Course is the primary key of the relation GRADE. (Entity Integrity) Roll No in the relation GRADE (child table) is a foreign key, which is referenced from the relation STUDENT (parent table). (Referential Integrity).
What is Multivalued Attribute? Multivalued Attribute - Multivalued attribute might have more than one value for an entity. For instance, PreviousDegrees of a STUDENT.
Explain weak and strong entity sets? Weak and Strong entity sets: A physically powerful entity set has a primary key. All tuples in the group are distinguishable through that k
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example of embedded SQL query
In a relational model how relations are termed? In a relational model, relations are termed as tables. (The term ‘relation’ is the technical name of the ‘table’ in RDBMS)
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What is the use of unique function? UNIQUE function: If UNIQUE is specified then only unique values are used to computed the mean.
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