DBMS Interview Questions And Answers For Frehsers

by Unknown Monday, January 30, 2012 0 comments 2012 dbms freshers placements questions sample papers Tips and Tricks

BASIC DBMS INTERVIEW QUESTIONS AND ANSWERS FOR FRESHERS

Data base management system (DBMS) is software, which is a collection ofprograms that enable user to create, modify, alter and delete the data. There are different types of DBMS ranging from small systems to mainframes used for huge process. Storing data can also be done using files but DBMS allows you to save the data easily and access it easily by providing security, reducing redundancy. Thus resulting data integrity, maintaining data base.

(Q) Describe the level of data abstraction?
(A) There are three levels for data abstraction
Physical level: The lowest level of abstraction describes how data are stored
Logical level: Next higher level in abstraction, describes which data is stored and relation between them
View Level: This describes the part of entire database

(Q) List the advantages of DBMS?
(A) Here is the list of advantages of using DBMS
1. Redundancy is controlled. (Duplication is controlled)
2.  Unauthorized access is restricted. (Restriction others to access data base information)
3. Providing multiple user interfaces. (Providing multi user access also limiting their permission)
4. Enforcing integrity constraints.
5.  Providing backup and recovery. (Back memory provided when data base crash occurs)

(Q) What is DBMS?
(A) DBMS is software that provides the user process of defining, creating, altering the data for various applications.

(Q) When we give SELECT * FROM EMP; How does oracle respond:
(A) When we ask the query SELECT * FROM EMP; the database server check all the data in the EMP file and it displays the data of the EMP file on the screen.

(Q) What is the difference between VARCHAR() and VARCHAR2()?
(A) Varchar means fixed length character data (size) i.e., min size-1 and max-2000
Varchar2 means variable (Dynamic) length character data i.e., min-1 to max-4000

(Q) Which command displays the SQL command in the SQL buffer, and then executes it?
(A) LIST or L command is used to get the recent one from SQL Buffer.

(Q) What is Difference between DBMS and File System?

(A) DBMS and File system are two ways of saving data, including managing data.

File System: It is a collection of raw data files stored in hard drive.

DBMS: It is a bundle of application that is dedicated for managing data stored in databases

In File System, files are used to store data while, collections of databases are utilized for the storage of data in DBMS. In file system storing altering data done manually. DBMS provide automated methods to complete managing data.

(Q) What is difference between DELETE and TRUNCATE?

(A) Both the commands are used to delete or remove the data from table, where as TRUNCATE is a DDL command and it can`t be rolled back. DELETE is a DML command and it can be roll back.

TRUNCATE deletes the data permanently while using DELETE  we can again get back the data.(ROLL back).

(Q) What is advantage of using trigger?

(A) Trigger used when we need to validate a DML statement that modifies a table. Also to update automatically when DML command is executed. Triggers can be used to enforce constraints.

(Q) What is use of WITH GRANT OPTION and GRANT command?

(A) These commands give privilege to grant his/her privileges to other users.

(Q) What is difference between SQL and SQL SERVER?

(A) SQL (sequel) is a language that provides an interface to RDBMS, developed by IBM. SQL SERVER is a RDBMS just like Oracle, DB2.

(Q) Write a query to find second maximum value from a table?

(A) select max (sal) from tname where sal= (select max (sal) from tname where sal< (select max (sal) from tname);

(Q) Write a query that returns only duplicate rows with number of times they are repeated, if table has duplicate values?

(A) SELECT COL1 FROM TAB1 WHERE COL1 IN (SELECT MAX (COL1) FROM TAB1 GROUP BY COL1 HAVING COUNT (COL1) > 1)