Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Before we talk about the relational model in more detail, let us first define some very basic terms used in this model.
Tuple
Every row in a table shows a record and is called a tuple. A table containing 'n' attributes in a record is called n-tuple.
Attribute
The name of every column in a table is used to interpret its meaning and is known as an attribute. Every table is called a relation.
For instance, Figure shows a relation PERSON. The columns NAME, PERSON_ID, AGE and ADDRESS are the attributes of PERSON and every row in the table represents a separate tuple (record).
Relation Name: PERSON
PERSON_ID
NAME
AGE
ADDRESS
TELEPHONE
1
Sanjay Prasad
35
b-4,Modi Nagar
011-25347527
2
Sharad Gupta
30
Pocket 2, Mayur Vihar.
023-12245678
3
Vibhu Datt
36
c-2, New Delhi
033-1601138
Figure: An extended PERSON relation
State about the Use Case Diagram A use case diagram represents a set of use cases, actors and their relationships. These diagrams shall be used to model context or requirement
To eliminate duplicate rows (distinct operator) Example: SELECT DISTINCT DEPTNO FROM EMP;
What is a relationship called when it is maintained between two entities? A relationship is called Binary relationship when it is maintained between two entities.
What is nested relational model? The nested relational model is an extension of relational model in which domains might be either atomic or relation valued.
Define hot swapping? Hot swapping permits the removal of faulty disks and changes it by new ones without turning power off. Hot swapping decreases the mean time to repair.
Why older data models are being replaced by new data modelling 100 words accepted#
In Oracle what is system global area and how is it organized? The SGA is a collection of shared memory fields which along with the Oracle processes constitute an Oracle instan
Write a short note on built in function in QBE? Built in function in QBE: QBE involves various built in functions like AVG, MAX,MIN,SUM and CNT. We must prefix these operator
How can i turn a conceptual entity relationship diagram into a logical entity relationship diagram? what do i have to do with "mandetory or" and "optional or" relationships?
#question.what is mapping constraints and types?.
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd