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Let us now make the E-R diagram for the student database as per the explanation given in the previous section.
We can also states the overall logical structure of a database using ER model graphically with the help of an E-R diagram.
ER diagrams are composed of:
Figure: ER diagram of COLLEGE database
Describe Specialsation and generalization? Specialisation /generalization: This is a top down and bottom up approach to the design of database. It displays the IS_A relation
Explain CNT in the respects of QBE ? CNT: It is one of the aggregation commands given in QBE. It is used to identify number of tuples
Consider the relation PERSON. If you want to display details of persons having age less than or equal to 30 than the select operation will be used as follows: σ AGE The resu
Competition entrants can be either Individuals, or Teams. A Team is usually sponsored by a business, and, in that case, the team members would all wear T-shirts with the sponsoring
What subschema expresses ? A subschema expresses the external view. (External schemas are called also called as subschemas)
Wait-die" scheme : The idea is based on non-preventive method. It is based on a simple rule: If Ti requests a database resource that is held by T
Discuss along with examples about several types of attributes present in the ER model? Types of Attributes are: • SIMPLE attributes are attributes which are drawn from the ato
#question.explain diversity and magnitude of organic compounds and general properties?
Consider the relation schemas as follows. works (person name, company name, salary); lives (person name, street, city); located in(company name, city); managers (person name
what is specialization?
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