viewquestions/12424/List the summary of the notations for ER diagrams Include symbols used in ER diagram and their meaning Database Management Systems 10CS54 VTU notes 8 Marks Jun July2014Jan 2016

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Asked by:anonymousguy7799

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Super key: A set of attributes SK of R such that no two tuples in any valid relation instance r(R) will have the same value for SK. That is, for any distinct tuples t1 and t2 in r(R), for any two distinct tuples t1 and t2 in a relation state r of R we have (the subset of attributes SK is called a superkey of the relation schema R).

 Domain: A set/universe of atomic values, where by “atomic” we mean simply that from the point of view of the database each value in the domain is indivisible.
 Tuple: A tuple is a mapping from attributes to values drawn from the respective domains of those attributes. A tuple is intended to describe some entity in the miniworld. 
Nulls: The null value is don’t know, not applicable Relational database schema: It is a set of schemas for its relations together with a set of integrity constraints.
Entity integrity constraint: The entity integrity constraint states that no primary key value can be null. This is because the primary key value is used to identify individual tuples in a relation: having null values for the primary keys implies that we cannot identify some tuples. Key constraints and entity constraints are specified on individual relations. 

Answerd By:Nikhil-bharadwaj

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