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Explain Relational model and their use in DBMS?
Relational Model - The relational model was first introduced through E.F. Codd of the IBM Research in the year of 1970. The model uses the concept of a mathematical relation (like a table of values) as its primary building block, and has its theoretical basis in set theory and first-order predicate logic. The relational model presents the database as a collection of relations.
Question: (a) Why is it important to know the architecture rather than to start requirement capture when designing a large scale system? (b) Who are the different people in
The natural join is equal to which product? The natural join is equal to Combination of projection and Cartesian product
What is the aim of object design The aim of object design is to identify object which the system contains and the interactions among them. The system implements specification
What is the main difference between read-only and update methods? A read-only method does not affect the values of a variable in an object, whereas an update method may alter t
ALTER TABLE Command : This command is used for variation of existing structure of the table in the given situation: When a new column is to be added to the table structure.
Object-based Models: Use objects as key data representation components . Examples:- Entity-Relationship Model: It is a collection of real world objects known as entitie
Define average seek time. The average seek time is the average of the seek times, calculated over a sequence of random requests.
UNION If R1 and R2 are two union compatible relations then R3 = R1 ∪ R2 is the relation having tuples that are either in R1 or in R2 or in both. In case, R3 will have tuples
Entity types that do not have any key attribute, and therefore cannot be identified independently, are known as weak entity types. A weak entity can be recognized uniquely only by
What is foreign key? A relation schema r1 derived from an ER schema may contain among its attributes the primary key of another relation schema r2.this attribute is known as a
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