DBMS Short Question And Answer Set-3

1. Define the terms i) DDL ii) DML
DDL: Data base schema is specified by a set of definitions expressed by a special language called a data definition language.
DML:A data manipulation language is a language that enables users to access or manipulate data as organized by the appropriate data model

 

2. What is embedded SQL? What are its advantages? 
Embedded SQL is a method of combining the computing power of a programming language and the database manipulation capabilities of SQL. Embedded SQL statements are SQL statements written in line with the program source code of the host language. The embedded SQL statements are parsed by an embedded SQL preprocessor and replaced by host-language calls to a code library. The output from the preprocessor is then compiled by the host compiler. This allows programmers to embed SQL statements in programs written in any number of languages
such as: C/C++, COBOL and Fortran

 

3. Write short notes on relational model
The relational model uses a collection of tables to represent both data and the relationships among those data. The relational model is an example of a record based model.

 

4. Define tuple and attribute

  • Attributes: column headers
  • Tuple : Row

 

5. Define the term relation.
Relation is a subset of a Cartesian product of list domains.

 

6. Define tuple variable
Tuple variable is a variable whose domain is the set of all tuples.

 

7. Define the term Domain.
For each attribute there is a set of permitted values called the domain of that attribute.

 

8. What is a candidate key?
Minimal super keys are called candidate keys.

 

9. What is a primary key?
Primary key is chosen by the database designer as the principal means of identifying an entity in the entity set.

 

10. What is a super key?
A super key is a set of one or more attributes that collectively allows us to identify uniquely an entity in the entity set.

 

11. List the table modification commands in SQL?

  • Deletion
  • Insertion
  • Updates
  • Update of a view

 

12. What are the ACID properties?
(atomicity, consistency, isolation, durability) is a set of properties that guarantee database transactions are processed reliably. In the context of databases, a single logical operation on the data is called a transaction. For example, a transfer of funds from one bank account to another, even though that might involve multiple changes (such as debiting one account and crediting another), is a single transaction.

 

13. What are two pitfalls (problem) of lock-based protocols? 

  • Deadlock
  • Starvation

 

14. What is transaction?
Collections of operations that form a single logical unit of work are called transactions.

 

15. What are the two statements regarding transaction?
The two statements regarding transaction of the form:

  • Begin transaction
  • End transaction

 

16. What are the properties of transaction?
The properties o f transactions are:

  • Atomicity
  • Consistency
  • Isolation
  • Durability

 

17. What is recovery management component?
Ensuring durability is the responsibility of a software component of the base system called the recovery management component.

 

18. When is a transaction rolled back?
Any changes that the aborted transaction made to the database must be undone. Once the changes caused by an aborted transaction have been undone, then the transaction has been rolled back.

 

19. What are the states of transaction?
The states of transaction are

  • Active
  • Partially committed
  • Failed
  • Aborted
  • Committed
  • Terminated

 

20. List out the statements associated with a database transaction?

  • Commit work
  • Rollback work