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Explain Record Based Logical Models?
Record-Based logical Models: Also define data at the conceptual and view levels. Unlike object-oriented models, are used to state overall logical structure of the database, and gives a higher-level description of the implementation. Named so since the database is structured in fixed-format records of various types. Each record type defines a fixed number of fields, or attributes. Each field is commonly of a fixed length (this simplifies the implementation). Record-based models do not involved a mechanism for direct representation of code in the database. Separate languages related along with the model are used to express database queries and updates. The three most widely-accepted models are the relational, network, and hierarchical.
One-way Associations When an association is traversed only in the one direction, then it is implemented as a pointer i.e.an attribute which contains an object reference. If mu
Security: In a centralised system, access to the data can be simply controlled. Though, in a distributed DBMS not only does access to replicated data have to be controlled in many
What is Message switching Message switching transmits data units which can be arbitrarily long. Packet switching has a utmost packet size, if any message longer than that, it s
Improved performance: As the data is located near the site of its demand, and given the inherent parallelism because of multiple copies, speed of database access may be good for di
Question: (a) What are decision support systems, and what role do they play in the business environment? (b) Data mining is a knowledge discovery process of automated extr
In a Hierarchical model of data records are organized ? In the hierarchical model of data records are organized as Tree structure.
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
E-R model uses this symbol to represent weak entity set ? A Doubly outlined rectangle symbol is used to represent weak entity set.
(A) For the relation; CarSales (RegNo, BuyerName, Address, SalesPerson, Make, Model, Commission) The following functional dependences hold, RegNo _ID à Make, Model Reg
deffine class&object
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