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!
It defines that no primary key value can be null. This is as the primary key is used to recognize individual tuple in the relation. So we will not be able to recognize the records uniquely containing null values for the primary key attributes. This constraint is specified on single individual relation.
Example: Let R be the Table
A#
B
C
Null
B1
C1
A2
B2
C2
B3
C3
A4
B4
A5
C5
Note:
1) '#' shows the Primary key of a relation.
In the relation R above, the primary key has null values in the tuples t1 & t3. NULL value in primary key is not allowed, therefore, relation instance is an invalid instance.
A super key is an attribute or set of attributes used to recognize the records uniquely in a relation. For instance, in the Relation PERSON defines earlier PERSON_ID is a super
Examples:- Hierarchical Model: It tells data as and relationships by hierarchy of data values. Figure illustrates an example of hierarchical model. Now a day's these models are
Homework chapter 10 no 3
When a function module is activated syntax checking is performed automatically. YEs, a function module is activated syntax checking.
Explain concept of inheritance with support of suitable example. Inheritance Inheritance is one of milestone of object-oriented programming language as it allows a creati
Define query optimization. Query optimization refers to the process of search the lowest -cost method of evaluating a given query.
Strong entity set and weak entity set? Strong entity set and weak entity set: A strong entity set has a primary key. All tuples in the set are distinguishable through that key.
WHAT IS DSS? WRITE ITS REQUIREMENTS.
Equi Join: A join in which the joining condition is based on equality among values in the common columns. Common columns show (redundantly) in the result table. Let us Consider th
diagrams and meaning
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