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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 of tables.
Constraints are stored in a meta-data table. This is a very easy model and is based on a proven mathematical theory. This is the most usually used data base model.
Network Model: In this model data is shown as records and relationship as links. A easy network model example is explained in Figure . It shows a sample diagram for such a system. This model is a very good quality model as far as conceptual framework is concerned but is today not used in database management systems.
Consider the following relational scheme: R (a,b,c,d,e,f) and its corresponding set of FDs {d→ a, be → c, ac → e, b → f, f → d, a → c}. a. Is the following decomposition i) non
What is substitutability? Any method of a class-say A can equally well be adjured with any object belonging to any subclasses B of A. This characteristic leads to code reuse, a
Assignment #1 Data Management The questions on this exam are based on the Baxter Aviation case scenario. 1. (5 points) The systems analyst proposes the following two relationshi
management information system based on functional organisation
What are the various symbols used to draw an E-R diagram? Explain with the help of an example how weak entity sets are represented in an E-R diagram. Various symbols used to d
Outer Join: The use of Outer Join is that it still joins those tuples that do not have matching values in common columns are also contained in the result table. Outer join places
(a) Why did SAP introduce the extended star schema?
When every condition appears with equality condition (=) only. c) Natural join (denoted by R*S) When two join attributes have the similar name in both relations. (Tha
Consider the following relations: S (S#, SNAME, STATUS, CITY) SP (S#, P#, QTY) P (P#, PNAME, COLOR, WEIGHT, CITY) Give an expression within SQL for each of queries b
What is Secondary Index While making the index, generally the index table is kept in the primary memory (RAM) and the main table, because of its size is keeps in the secondary
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