It is possible to write tuple calculus expressions that generate infinite relations. For example {t/~te R} results in an infinite relation if the domain of any attribute of relation R is infinite. To guard against the problem, we restrict the set of allowable expressions to safe expressions.
Mwalimu Bonface answered the question on March 1, 2018 at 10:33
- What do you understand by domain integrity constraint? (Solved)
What do you understand by domain integrity constraint?
Date posted: March 1, 2018. Answers (1)
- What are the advantages of QBE? (Solved)
What are the advantages of QBE?
Date posted: March 1, 2018. Answers (1)
- A union, intersection or difference can only be performed between two relations if they are type compatible. What is meant by type compatibility? Give an...(Solved)
A union, intersection or difference can only be performed between two relations if they are type compatible. What is meant by type compatibility? Give an example of two type compatible and two non type compatible relations?
Date posted: March 1, 2018. Answers (1)
- Bring out the reasons why relational model became more popular? (Solved)
Bring out the reasons why relational model became more popular?
Date posted: March 1, 2018. Answers (1)
- Mention the pros and cons of relational data model?(Solved)
Mention the pros and cons of relational data model?
Date posted: March 1, 2018. Answers (1)
- Give an example of supertype/subtype relationship where the overlap rule applies?(Solved)
Give an example of supertype/subtype relationship where the overlap rule applies?
Date posted: March 1, 2018. Answers (1)
- What is inheritance in generalization hierarchies? (Solved)
What is inheritance in generalization hierarchies?
Date posted: March 1, 2018. Answers (1)
- Guidelines for designing a good pseudo code. (Solved)
Guidelines for designing a good pseudo code.
Date posted: February 28, 2018. Answers (1)
- Explain the meaning of “what if analysis” in spreadsheets(Solved)
Explain the meaning of “what if analysis” in spreadsheets
Date posted: February 28, 2018. Answers (1)
- Distinguish between Hard system and soft system(Solved)
Distinguish between Hard system and soft system
Date posted: February 28, 2018. Answers (1)
- State two reasons for partitioning a disk. (Solved)
State two reasons for partitioning a disk.
Date posted: February 28, 2018. Answers (1)
- Differentiate between partitioning and formatting as used in disk management.(Solved)
Differentiate between partitioning and formatting as used in disk management.
Date posted: February 28, 2018. Answers (1)
- Define the following features of a desktop:(a)icons (b)task bar (c)background (d)recycle bin(Solved)
Define the following features of a desktop:
(a)icons
(b)task bar
(c)background
(d)recycle bin
Date posted: February 28, 2018. Answers (1)
- Differentiate between Entity type and Entity set. (Solved)
Differentiate between Entity type and Entity set.
Date posted: February 28, 2018. Answers (1)
- Define entity as used in DBMS with example? (Solved)
Define entity as used in DBMS with example?
Date posted: February 28, 2018. Answers (1)
- Define the concept of “database schema.” Describe the types of schemas
that exist in a database complying with the three levels ANSI/SPARC architecture.(Solved)
Define the concept of “database schema.” Describe the types of schemas
that exist in a database complying with the three levels ANSI/SPARC architecture.
Date posted: February 28, 2018. Answers (1)
- What is poor email etiquette?(Solved)
What is poor email etiquette?
Date posted: February 28, 2018. Answers (1)
- What the name for the program or service that lets you view e-mail messages?(Solved)
What the name for the program or service that lets you view e-mail messages?
Date posted: February 28, 2018. Answers (1)
- With the use of internet, email has become part and parcel of communication. Briefly describe the negative impact it brings.(Solved)
With the use of internet, email has become part and parcel of communication. Briefly describe the negative impact it bring.
Date posted: February 28, 2018. Answers (1)
- The internet is making the world to be a global village with easier communication of email. Describe the advantages of using email for communication.(Solved)
The internet is making the world to be a global village with easier communication of email. Describe the advantages of using email for communication.
Date posted: February 28, 2018. Answers (1)