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.
Mappings between Levels and Data Independence The 3 levels of abstraction in the database do not exist separately of each other. There must be some correspondence, or mapping
Explain about primary key Primary Key: It is one of the candidate keys that are taken to be the recognizing key for the entire table. E.g. although there are two candidate ke
We face problem of stock Opening balance and closing balance in Minus
What are advantages of object models? Object models are efficient for communicating with the application experts and reaching a consensus about the significant aspects of the p
explain five responsibilities of DBA?
what is natural join?
ddlc
Is it mandatory to declare all the tables in Report by the key word tables for all the tables that exist in the structure of LDB, and are being explained in the Database part of LD
Question 1 Explain the 10 reasons to use MySQL Question 2 Write the SQL statements to demonstrate the following using SELECT command Expression Evaluation ORDER BY
explain equi-join using illustration
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