MOST IMPORTANT QUESTIONS AND CONCEPTS OF
INTRODUCTION OF DBMS
1. What is Database?
A database is a collection of related ,logically coherent data used by the application programs in an organization.
2. What is DBMS?
A DBMS is a collection of interrelated data and a set of programs to access those data.
3. What are the functions of DBMS?
defining, constructing, manipulating and sharing
4. Name the people who are participating in DBMS.
DBMS implementer, Database designer, Database application developer and Database administrator
5 Difference between File system and Database System.
1. Data redundancy: Same information is duplicated in File system where as in Database system no information is duplicated.
2. Difficulty in Accessing data : In File system we face difficulty in accessing through programs whereas in Database System we access through simple queries.
3. Security: DBMS Provides good protection mechanism whereas in File system is not.
4. Concurrency: Database handle concurrency whereas in file system is not.
6. Define Schema and Instance
Schema – the logical structure of the database
Instance – the actual content of the database at a particular point in time
7. Three Schema Architecture
8. State two types of Independence
Physical Data Independence – the ability to modify the physical schema without changing the logical schema
Logical Data Independence- the ability to modify the logical schema without having to change external schema or application programs.
9. Various Data Models (Only Models are important Not definitions)
- Hierarchical model
- Network model
- Relational model
- The object oriented model
- The object relational model
Relational database model In the relational model, data is organized in 2-D tables called relations. The tables or relations are, however, related to each other.
11. What are the types of Database languages?
12. Most Important DDL(Database Definition Language) Commands (Drop, Delete and Truncate are most most important)
Database Definition Language ---Use to define database structure & schema
CREATE : to create object in DB
ALTER: alters the structure of DB
DROP: delete object from DB
TRUNCATE: remove all record from table
COMMENT: add comment to data dictionary
RENAME: rename an object
13. Most Important DDL(Database Manipulation Language) Commands.
Database Manipulation language ---- To modify data
SELECT: to retrieve data from DB
INSERT: insert data to table
UPDATE: update existing data within a table
DELETE: delete rows from table
CALL: call a PL/SQL or java program
14. Most Important DCL AND TCL LANGUAGE
DCL (DATA CONTROL LANGUGAE)
GRANT: gives users access privileges to DB
REVOKE: withdraw access privileges given with the GRANT command
TCL (TRANSACTION CONTROL LANGUAGE)
COMMIT: save work done
ROLLBACK: restore DB to original state since last commit.
SAVEPOINT: identify a point in transaction to which you can later rollback
15. What are Database Users (Naive User Most Important)
Database Users --Users are differentiated by the way they expect to interact with the system
Application programmers – interact with system through DML calls, writes application programs
Sophisticated users – form requests in a database query language eg analysts
Specialized users – write specialized database applications that do not fit into the traditional data processing framework
Naïve users – invoke one of the permanent application programs that have been written previous
16. What is Storage Manager?
Provide interface between low level data in database and application program.
17. Query processor (M.Imp.)
Query Processor • DDL interpreter: which interprets DDL statements and records the definitions in the data dictionary
DML Compiler: translate DML statements to evaluation plan. Also perform query optimization. (pick the lowest cost evaluation plan from among the alternatives)
Query Evaluation Engine: executes low level instructions generated by DML compiler.
18. 2- Tier Architecture
){kind=link}
0 Comments