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What is the difference between a key and a superkey?
Key - A key a single attribute or a combination of two or more attributes of an entity set which is used to identify one or more examples (rows) of the set (table). It is a minimal combination of attributes.
Super Key - A super key is a set of one or more attributes in which, taken collectively, permits us to identify uniquely a tuple within the relation.
(a) What is a Sub-Query? (b) What is the difference between a scalar sub-query and a tabular sub-query? (c) Write an equivalent SQL statement to get the Name of Product wh
Describe the storage structure of indexed sequential files and their access method. Ans: Index offers a lookup capability to rapidly reach the vicinity of the desired record.
Record based Logical Models: Use records as the key data representation components Examples: Relational Model: It shows data as well as relationship between data in the form
How external/conceptual mapping and conceptual /internal mapping is performed
under what condition log based recovery is feasible?
Illustrate the statement 'Projection operation distributes over the union operation'. Give an example. Ans: Π L (E 1 ∪ E 2 ) = (Π L (E 1 )) ∪ (Π L (E 2 )) This says th
Give the general form of SQL query? Select A1, A2............., An From R1, R2..............., Rm Where P
does tables are called relations
why are older data models are being replaced by new data models
What do you understand by transitive dependencies? Define with an example any two problems that can take place in the database if transitive dependencies are available in the datab
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