In this page, I will explained short answer type questions of 12th Class RDBMS unit. In this, you will learn all types of questions answers related to Database. These questions are very important for IT(Information Technology) Exam under CBSE and Haryana Board. These questions will prove to be very good for your exam.
12th Class RDBMS Questions Answer
Q:- What is Data and Information?
Ans:- Data is a collection of raw facts which have not been processed to reveal useful information. Information is produced by processing data.
Q:- What is DBMS?
Ans:- A database management system is a collection of programs that enables users to create, maintain and use a database.
Q:- Why Need for a DATABASE?
Ans:- In traditional file processing, data is stored in the form of files. A number of application programs are written by programmers to insert, delete, modify and retrieve data from these files. New application programs will be added to the system as the need arises. For example, consider the Sales and Payroll departments of a company. One user will maintain information about all the salespersons in the Sales department in some file say File1 and another user will maintain details about the payroll of the salesperson in a separate file say File2 in the Payroll Department.
Although both the departments need information about the salesperson but they will store information about the salesperson in different files and will use different application programs to access those files. This would result in:
1. Data Redundancy: Same information is stored in more than one file. This would result in wastage of space.
2. Data Inconsistency: If a file is updated then all the files containing similar information must be updated else it would result in inconsistency of data.
3. Lack of Data Integration: As data files are independent, accessing information out of multiple files becomes very difficult.
Q:- What operations are needed for the database to perform?
Ans:- The various operations that need to be performed on a database are as follows:
1. Defining the Database: It involves specifying the data type of data that will be stored in the database and also any constraints on that data.
2. Populating the Database: It involves storing the data on some storage medium that is controlled by DBMS.
3. Manipulating the Database: It involves modifying the database, retrieving data or querying the database, generating reports from the database etc.
4. Sharing the Database: Allow multiple users to access the database at the same time.
5. Protecting the Database: It enables protection of the database from software/ hardware failures and unauthorized access.
6. Maintaining the Database: It is easy to adapt to the changing requirements. Some examples ofDBMS are – MySQL, Oracle, DB2, IMS, IDS etc.
Q:- What are the Characteristics of Database Management System?
Ans:- There are so many characteristics of a database management system, which are as follows −
- A database management system is able to store any kind of data in a database.
- The Database management system allows so many users to access databases at the same time.
- Backup and recovery are the two main methods which allow users to protect the data from damage or loss.
- It also provides multiple views for different users in a single organization.
- It follows the concept of normalization which is helpful to minimize the redundancy of a relation.
- It also provides users query language, helpful to insert, retrieve, update, and delete the data in a database.
Q:- Write the types of users of DBMS?
Ans:- DBMS is used by many types of users depending on their requirements and interaction with
the DBMS. There are mainly four types of users:
1. End Users
2. Database Administrator (DBA)
3. Application Programmers
4. System Analyst
12th Class RDBMS Questions Answer
Q:- Write the Advantages and Disadvantages of DBMS.
Ans:- The need of DBMS itself explains the advantages of using a DBMS. Following are the advantages ofusing a DBMS:
Advantages of DBMS
1. Reduction in Redundancy: Data in a DBMS is more concise because of the central repository of data. All the data is stored at one place. There is no repetition of the same data. This also reduces the cost of storing data on hard disks or other memory devices.
2. Improved Consistency: The chances of data inconsistencies in a database are also reduced as there is a single copy ofdata that is accessed or updated by all the users.
3. Improved Availability: Same information is made available to different users. This helps sharing of information by various users of the database.
4. Improved Security: Though there is improvement in the availability of information to users, it may also be required to restrict the access to confidential information. By making use of passwords and controlling users’ database access rights, the DBA can provide security to the database.
5. User Friendly: Using a DBMS, it becomes very easy to access, modify and delete data. It reduces the dependency of users on computer specialists to perform various data related operations in a DBMS because of its user friendly interface.
Disadvantages or Limitations of DBMS
The two main disadvantages of using a DBMS:
1. High Cost: The cost of implementing a DBMS system is very high. It is also a very time consuming process which involves analyzing user requirements, designing the database specifications, writing application programs and then also providing training.
2. Security and Recovery Overheads: Unauthorized access to a database can lead to threat to the individual or organization depending on the data stored. Also the data must be regularly backed up to prevent its loss due to fire, earthquakes, etc.
Q:- What is RDBMS ?
Ans:- RDBMS stands for Relational Database Management System. RDBMS is the basis for SQL, and for all modern database systems like MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.
A Relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd.
Q:- What is a Record or a Row?
Ans:- A record is also called as a row of data is each individual entry that exists in a table.
Q:- What is a Column or Field?
Ans:- A column is a vertical entity in a table that contains all information associated with a specific field in a table.
Q:- What is Key ?
Ans:- A column or a combination of columns which can be used to identify one or more rows
(tuples) in a table is called a key of the table.
Q:- What is Primary Key?
Ans:- The group of one or more columns used to uniquely identify each row of a relation
is called its Primary Key.
Q:- What is Candidate Key?
Ans:- A column or a group of columns which can be used as the primary key of a
relation is called a Candidate key because it is one of the candidates available to be the primary
key of the relation.
Q:- What is Alternate Key?
Ans:- A candidate key of a table which is not selected as the primary key is called its Alternate Key.
Q:- What is Foreign Key?
Ans:- A primary key of a base table when used in some other table is called as Foreign Key.
12th Class RDBMS Questions Answer
Q:- What is NULL Value?
Ans:- A NULL value in a table is a value in a field that appears to be blank, which means a field with a NULL value is a field with no value.
Q:- What is Composite Key?
Ans:- A composite key in SQL can be defined as a combination of multiple columns, and these columns are used to identify all the rows that are involved uniquely. Even though a single column can’t identify any row uniquely, a combination of over one column can uniquely identify any record.
Q:- What is SQL ?
Ans:- SQL is a language that is used to manage data stored in a RDBMS. It comprises of a Data Definition Language (DDL) and a Data Manipulation Language (DML) where DDL is a language which is used to define structure and constraints of data and DML is used to insert, modify and delete data in a database.
Q:- Write the Characteristics of SQL
Ans:- MySQL is released under an open-source license so it is customizable.
- It requires no cost or payment for its usage.
- MySQL has superior speed, is easy to use and is reliable.
- MySQL uses a standard form of the well-known ANSI-SQL standards.
- MySQL is a platform independent application which works on many operating systems like
Windows, UNIX, LINUX etc. and has compatibility with many languages including JAVA , C++,
PHP, PERL, etc.
- MySQL is an easy to install RDBMS and is capable of handling large data sets.
Q:- What is MYSQL?
Ans:- MySQL is an open source SQL database, which is developed by a Swedish company. MySQL is supporting many different platforms including Microsoft Windows, the major Linux distributions, UNIX, and Mac OS X.
Q:- What is a DDL command?
Ans:- DDL stands for Data Definition Language. As the name suggests, the DDL commands help to define the structure of the databases or schema. When we execute DDL statements, it takes effect immediately. The changes made in the database using this command are saved permanently because its commands are auto-committed. The following commands come under DDL language:
- CREATE: It is used to create a new database and its objects such as table, views, function, stored procedure, triggers, etc.
- DROP: It is used to delete the database and its objects, including structures, from the server permanently.
- ALTER: It’s used to update the database structure by modifying the characteristics of an existing attribute or adding new attributes.
- TRUNCATE: It is used to completely remove all data from a table, including their structure and space allocates on the server.
- RENAME: This command renames the content in the database.
Q:- What is a DML command?
Ans:- It stands for Data Manipulation Language. The DML commands deal with the manipulation of existing records of a database. It is responsible for all changes that occur in the database. The changes made in the database using this command can’t save permanently because its commands are not auto-committed. Therefore, changes can be rollback. The following commands come under DML language:
- SELECT: This command is used to extract information from a table.
- INSERT: It is a SQL query that allows us to add data into a table’s row.
- UPDATE: This command is used to alter or modify the contents of a table.
- DELETE: This command is used to delete records from a database table, either individually or in groups.
Q:- How many Types of SQL Data Type?
Ans:- SQL Data Type is an attribute that specifies the type of data of any object. Each column, variable and expression has a related data type in SQL. You can use these data types while creating your tables. You can choose a data type for a table column based on your requirement.
|CHAR[Length]||Length bytes||A fixed-length Field From 0 to 255 characters long.|
|VARCHAR(Length)||String length + 1 bytes||A fixed-length Field From 0 to 255 Characters long.|
|INT[Length]||4 bytes||Range of -2,147,483,648 to 2,147,483,647 or 0 to 4,294,967,295 unsigned.|
|DECIMAL[Length, Decimals]||Length + 1 or Length + 2 bytes||A DOUBLE Stored as a string, Allowing for a Fixed Decimal Point|
|DATE||3 bytes||In the format of YYYY-MM-DD.|
|DATETIME||8 bytes||In the format of YYYY-MM-DD HH:MM:SS.|
|TIMESTAMP||4 bytes||In the format of YYYYMMDDHHMMSS; acceptable range ends inthe year 2037.|
|TIME||3 bytes||In the format of HH:MM:SS|
Q:- How to Create a Database & Table in DBMS Software?
Ans:- Creating a Database
Before creating a table we will first create a database. To create a database we will give
CREATE DATABASE command.
mysql> CREATE DATABASE School;
Once the above mentioned statement gets executed, a database with the name School is created on system. You may give any name of the database . Now to open the database to work USE statements are required. ! Semicolon is standard way to end SQL statement.
Creating a Table
After creating a database, the next step is creation of tables in the database. For this CREATE TABLE statement is used.
Create a simple table named Learner with only two columns RollNo and Name in the School database.
To do this, enter the following statement:
mysql> CREATE TABLE Learner
Q:- What is Constraints in Table?
Ans:- Many times it is not possible to keep a manual check on the data that is going into the tables. The data entered may be invalid. MySQL provides some rules, called Constraints, which help us, to some extent, ensure validity of the data. These constraints are:
|Primary Key||Sets a column or a group of columns as a primary key of the table. Therefore, NULLs and Duplicate values in this column are not accepted.|
|NOT NULL||Makes sure that NULLs are not accepted in the specified column.|
|FOREIGN KEY||Data will be accepted in this column, if the same data value exists in a column in another related table. This other related table name and column name are specified while creating the foreign key constraint.|
|UNIQUE||Make sure that duplicate values in the specified column are not accepted.|
Q:- How to Record Insert, Delete and Modify in Table?
Ans:- INSERT COM M AND
After creating database and relations, we can add data in the relations. INSERT INTO command
is used to enter values in a table. Syntax of insert command is as follows :
INSERT INTO <TABLENAME >(COLUMN NAMES>) VALUES (value1, value2, value3,……)
INSERT command is used in various ways to insert values within a table. Following points should
be kept in mind while inserting records in a relation. :
– Numeric values may be entered as numerals
– string must be enclosed in single/ double quotes
– Date should be entered in single/double quotes in format ‘yyyy -mm-dd’
– NULL value should be entered as NULL without any quotes. NULL value means blank value in
For example :
mysql> INSERT INTO STUDENT(RNO,GENDER, LNAME,FNAME) VALUES(8,’F’,’SHANU’,
SELECT COM M AND :
SELECT command is used to view the data from a relation in a database. It returns a result set of
data/ records from one or more relations.
Syntax of SELECT Command :
SELECT <column name> FROM <table name >;
A select statement can also be used with the insert command provided, the result of select
query is of the same order as the given list of columns
Command to retrieve single column display
select Rno from STUDENT;
UPDATE command is used to modify data of records within the table. It is a type of DML and is
used to make changes in the values entered in the table :
UPDATE <table name>
SET <column name> = <value>, [<column name> = <value> , …]
[WHERE <condition> ];
The command can be used to update one or more columns and WHERE clause is used for modifying the records that matches a criteria.
DELETE Command is used to remove records from the table.
Syntax of the command is :
DELETE from <table name>
Command to delete record of student whose roll number is 13.
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