CBSE Computer Science and Informatics Practices: CLASS XII COMPUTER SCIENCE CHAPTER 11 & 12 DATABASE AND SQL

CHAPTER 11& 12

DATABASE CONCEPTS AND SQL

Data :- Raw facts and figures which are useful to an organization. We cannot take decisions on the basis of data.

Information:- Well processed data is called information. We can take decisions on the basis of information.

Field: Set of characters that represents specific data element.

Record:Collection of fields is called a record. A record can have fields of different data types.

File: Collection of similar types of records is called a file.

Table: Collection of rows and columns that contains useful data/information is called a table.

A table generally refers to the passive entity which is kept in secondary storage device.

Relation:Relation (collection of rows and columns) generally refers to an active entity on which we can perform various operations.

Database:Collection of logically related data along with its description is termed as database.

Tuple: A row in a relation is called a tuple.

Attribute:A column in a relation is called an attribute. It is also termed as field or data item.

Degree:Number of attributes in a relation is called degree of a relation.

Cardinality:Number of tuples in a relation is called cardinality of a relation.

Primary Key:Primary key is a key that can uniquely identifies the records/tuples in a relation. This key can never be duplicated and NULL.

Foreign Key: Foreign Key is a key that is defined as a primary key in some other relation. This key is used to enforce referential integrity in RDBMS.

Candidate Key: Set of all attributes which can serve as a primary key in a relation.

Alternate Key: All the candidate keys other than the primary keys of a relation are alternate keys for a relation.

DBA: Data Base Administrator is a person (manager) that is responsible for defining the data base schema, setting security features in database, ensuring proper functioning of the data bases etc.

Structured Query Language

SQL is a non procedural language that is used to create, manipulate and process the databases(relations).

Characteristics of SQL

It is very easy to learn and use.
Large volume of databases can be handled quite easily.
It is non procedural language. It means that we do not need to specify the procedures to accomplish a task but just to give a command to perform the activity.
SQL can be linked to most of other high level languages that makes it first choice for the database programmers.

Processing Capabilities of SQL

The following are the processing capabilities of SQL

Data Definition Language (DDL)

DDL contains commands that are used to create the tables, databases, indexes, views, sequences and synonyms etc.

e.g: Create table, create view, create index, alter table etc.

Data Manipulation Language (DML)

DML contains command that can be used to manipulate the data base objects and to query the databases for information retrieval.

e.g Select, Insert, Delete, Update etc.

View Definition:

DDL contains set of command to create a view of a relation.

e.g :create view

Data Control Language:

This language is used for controlling the access to the data. Various commands like GRANT, REVOKE etc are available in DCL.

5. Transaction Control Language (TCL)

TCL include commands to control the transactions in a data base system. The commonly used commands in TCL are COMMIT, ROLLBACK etc.

Data types of SQL

Just like any other programming language, the facility of defining data of various types is available in SQL also. Following are the most common data types of SQL.

1) NUMBER

2) CHAR

3) VARCHAR / VARCHAR2

4) DATE

5) LONG

6) RAW/LONG RAW

1. NUMBER

Used to store a numeric value in a field/column. It may be decimal, integer or a real value. General syntax is

Number(n,d)

Where n specifies the number of digits and

d specifies the number of digits to the right of the decimal point.

e.g marks number(3) declares marks to be of type number with maximum value 999.

pct number(5,2) declares pct to be of type number of 5 digits with two digits to the right of decimal point.

2. CHAR

Used to store character type data in a column. General syntax is

Char (size)

where size represents the maximum number of characters in a column. The CHAR type data can hold at most 255 characters.

e.g name char(25) declares a data item name of type character of upto 25 size long.

3. VARCHAR/VARCHAR2

This data type is used to store variable length alphanumeric data. General syntax is

varchar(size) / varchar2(size)

where size represents the maximum number of characters in a column. The maximum allowed size in this data type is 2000 characters.

e.g address varchar(50); address is of type varchar of upto 50 characters long.

4. DATE

Date data type is used to store dates in columns. SQL supports the various date formats other that the standard DD-MON-YY.

e.g dob date; declares dob to be of type date.

5. LONG

This data type is used to store variable length strings of upto 2 GB size.

e.g description long;

6. RAW/LONG RAW

To store binary data (images/pictures/animation/clips etc.) RAW or LONG RAW data type is used. A column LONG RAW type can hold upto 2 GB of binary data.

e.g image raw(2000);

SQL Commands

a. CREATE TABLE Command:

Create table command is used to create a table in SQL. It is a DDL type of command. The general syntax of creating a table is

Creating Tables

The syntax for creating a table is

create table <table> (

<column 1> <data type> [not null] [unique] [<column constraint>],

. . . . . . . . .

<column n> <data type> [not null] [unique] [<column constraint>],

[<table constraint(s)>]

);

For each column, a name and a data type must be specified and the column name must be unique within the table definition. Column definitions are separated by comma. Uppercase and lowercase letters makes no difference in column names, the only place where upper and lower case letters matter are strings comparisons. A not null Constraint means that the column cannot have null value, that is a value needs to be supplied for that column. The keyword unique specifies that no two tuples can have the same attribute value for this column.

Operators in SQL:

The following are the commonly used operators in SQL

1. Arithmetic Operators +, -, *, /

2. Relational Operators =, <, >, <=, >=, <>

3. Logical Operators OR, AND, NOT

Arithmetic operators are used to perform simple arithmetic operations.

Relational Operators are used when two values are to be compared and Logical operators are used to connect search conditions in the WHERE Clause in SQL.

Constraints:

Constraints are the conditions that can be enforced on the attributes of a relation. The constraints come in play when ever we try to insert, delete or update a record in a relation.

NOT NULL
UNIQUE
PRIMARY KEY
FOREIGN KEY
CHECK
DEFAULT

Not null ensures that we cannot leave a column as null. That is a value has to be supplied for that column.

e.g name varchar(25) not null;

Unique constraint means that the values under that column are always unique.

e.g Roll_no number(3) unique;

Primary key constraint means that a column can not have duplicate values and not even a null value.

e.g. Roll_no number(3) primary key;

The main difference between unique and primary key constraint is that a column specified as unique may have null value but primary key constraint does not allow null values in the column.

Foreign key is used to enforce referential integrity and is declared as a primary key in some other table.

e.g cust_id varchar(5) references master(cust_id);

it declares cust_id column as a foreign key that refers to cust_id field of table master. That means we cannot insert that value in cust_id filed whose corresponding value is not present in cust_id field of master table.

Check constraint limits the values that can be inserted into a column of a table.

e.g marks number(3) check(marks>=0);

The above statement declares marks to be of type number and while inserting or updating the value in marks it is ensured that its value is always greater than or equal to zero.

Default constraint is used to specify a default value to a column of a table automatically. This default value will be used when user does not enter any value for that column.

e.g balance number(5) default = 0;

CREATE TABLE student (

Roll_no number(3) primary key,

Name varchar(25) not null,

Class varchar(10),

Marks number(3) check(marks>0),

City varchar(25) );

Data Modifications in SQL

After a table has been created using the create table command, tuples can be inserted into the table, or tuples can be deleted or modified.

INSERT Statement

The simplest way to insert a tuple into a table is to use the insert statement

insert into <table> [(<column i, . . . , column j>)] values (<value i, . . . , value j>);

INSERT INTO student VALUES(101,'Rohan','XI',400,'Jammu');

While inserting the record it should be checked that the values passed are of same data types as the one which is specified for that particular column.

For inserting a row interactively (from keyboard) & operator can be used.

e.g INSERT INTO student VALUES(&Roll_no’,’&Name’,’&Class’,’&Marks’,’&City’);

In the above command the values for all the columns are read from keyboard and inserted into the table student.

NOTE:- In SQL we can repeat or re-execute the last command typed at SQL prompt by typing “/” key and pressing enter.

Roll_no	Name	Class	Marks	City
101	Rohan	XI	400	Jammu
102	Aneeta Chopra	XII	390	Udhampur
103	Pawan Kumar	IX	298	Amritsar
104	Rohan	IX	376	Jammu
105	Sanjay	VII	240	Gurdaspur
113	Anju Mahajan	VIII	432	Pathankot

Queries:

To retrieve information from a database we can query the databases. SQL SELECT statement is used to select rows and columns from a database/relation.

SELECT Command

This command can perform selection as well as projection.

Selection:This capability of SQL can return you the tuples form a relation with all the attributes.

Projection: This is the capability of SQL to return only specific attributes in the relation.

*SELECT * FROM student; command will display all the tuples in the relation student

*SELECT * FROM student WHERE Roll_no <=102;

The above command display only those records whose Roll_no less than or equal to 102.

Select command can also display specific attributes from a relation.

*SELECT name, class FROM student;

The above command displays only name and class attributes from student table.

*SELECT count(*) AS “Total Number of Records” FROM student;

Display the total number of records with title as “Total Number of Records” i.e an alias

We can also use arithmetic operators in select statement, like

*SELECT Roll_no, name, marks+20 FROM student;

*SELECT name, (marks/500)*100 FROM student WHERE Roll_no > 103;

Eliminating Duplicate/Redundant data

DISTINCT keyword is used to restrict the duplicate rows from the results of a SELECT statement.

e.g. SELECT DISTINCT name FROM student;

The above command returns

Name

Rohan

Aneeta Chopra

Pawan Kumar

Conditions based on a range

SQL provides a BETWEEN operator that defines a range of values that the column value must fall for the condition to become true.

e.g. SELECT Roll_no, name FROM student WHERE Roll_no BETWENN 100 AND 103;

The above command displays Roll_no and name of those students whose Roll_no lies in the range 100 to 103 (both 100 and 103 are included in the range).

Conditions based on a list

To specify a list of values, IN operator is used. This operator select values that match any value in the given list.

e.g. SELECT * FROM student WHERE city IN (‘Jammu’,’Amritsar’,’Gurdaspur’);

The above command displays all those records whose city is either Jammu or Amritsar or Gurdaspur.

Conditions based on Pattern

SQL provides two wild card characters that are used while comparing the strings with LIKE operator.

a. percent(%) Matches any string

b.Underscore(_) Matches any one character

e.g SELECT Roll_no, name, city FROM student WHERE Roll_no LIKE “%3”;

displays those records where last digit of Roll_no is 3 and may have any number of characters in front.

e.g SELECT Roll_no, name, city FROM student WHERE Roll_no LIKE “1_3”;

displays those records whose Roll_no starts with 1 and second letter may be any letter but ends with digit 3.

ORDER BY Clause

ORDER BY clause is used to display the result of a query in a specific order(sorted order).

The sorting can be done in ascending or in descending order. It should be kept in mind that the actual data in the database is not sorted but only the results of the query are displayed in sorted order.

e.g. SELECT name, city FROM student ORDER BY name;

The above query returns name and city columns of table student sorted by name in increasing/ascending order.

e.g. SELECT * FROM student ORDER BY city DESC;

It displays all the records of table student ordered by city in descending order.

Note:- If order is not specifies that by default the sorting will be performed in ascending order.

GROUP BY Clause

The GROUP BY clause can be used in a SELECT statement to collect data across multiple records and group the results by one or more columns.

The syntax for the GROUP BY clause is:

SELECT column1, column2, ... column_n, aggregate_function (expression)
FROM tables
WHERE conditions
GROUP BY column1, column2, ... column_n;

aggregate_function can be a function such as SUM, COUNT, MAX, MIN, AVG etc.

e.g SELECT name, COUNT(*) as "Number of employees"
FROM student
WHERE marks>350
GROUP BY city;

HAVING Clause

The HAVING clause is used in combination with the GROUP BY clause. It can be used in a SELECT statement to filter the records that a GROUP BY returns.

The syntax for the HAVING clause is:

SELECT column1, column2, ... column_n, aggregate_function (expression)
FROM tables
WHERE predicates
GROUP BY column1, column2, ... column_n
HAVING condition1 ... condition_n;

e.g SELECT SUM(marks) as "Total marks"
FROM student
GROUP BY department
HAVING SUM(sales) > 1000;

Note: select statement can contain only those attribute which are already present in the group by clause.

Functions available in SQL

SQL provide large collection of inbuilt functions also called library functions that can be used directly in SQL statements.

1. Mathematical functions

2. String functions

3. Date & Time functions

1.Mathematical functions

Some of the commonly used mathematical functions are sum() avg(), count(), min(), max() etc.

e.g. SELECT sum(marks) FROM student;

displays the sum of all the marks in the table student.

e.g. SELECT min(Roll_no), max(marks) FROM student;

displays smallest Roll_no and highest marks in the table student.

2.String functions

These functions are used to deal with the string type values like

ASCII, LOWEWR, UPPER, LEN, LEFT, RIGHT, TRIM, LTRIM, RTRIM etc.

ASCII : Returns the ASCII code value of a character(leftmost character of string).

Syntax: ASCII(character)

SELECT ASCII('a') returns       97
SELECT ASCII('A') returns      65
SELECT ASCII('1') returns       49
SELECT ASCII('ABC') returns 65

For Upper character 'A' to 'Z' ASCII value 65 to 90
For Lower character 'A' to 'Z' ASCII value 97 to 122
For digit '0' to '9' ASCII value 48 to 57

NOTE: If no table name is specified then SQL uses Dual table which is a dummy table used for performing operations.

LOWER : Convert character strings data into lowercase.

Syntax: LOWER(string)

SELECT LOWER('STRING FUNCTION') returns string function

UPPER : Convert character strings data into Uppercase.

Syntax: UPPER(string)

SELECT UPPER('string function') returns STRING FUNCTION

LEN : Returns the length of the character string.

Syntax: LEN(string)

SELECT LEN('STRING FUNCTION') returns 15

REPLACE : Replaces all occurrences of the second string(string2) in the first string(string1) with a third string(string3).

Syntax: REPLACE('string1','string2','string3')

SELECT REPLACE('STRING FUNCTION','STRING','SQL') returns SQL Function

Returns NULL if any one of the arguments is NULL.

LEFT : Returns left part of a string with the specified number of characters counting from left.LEFT function is used to retrieve portions of the string.

Syntax: LEFT(string,integer)

SELECT LEFT('STRING FUNCTION', 6) returns STRING

RIGHT : Returns right part of a string with the specified number of characters counting from right.RIGHT function is used to retrieve portions of the string.

Syntax: RIGHT(string,integer)

SELECT RIGHT('STRING FUNCTION', 8) returns FUNCTION

LTRIM : Returns a string after removing leading blanks on Left side.(Remove left side space or blanks)

Syntax: LTRIM(string)

SELECT LTRIM(' STRING FUNCTION') returns STRING FUNCTION

RTRIM : Returns a string after removing leading blanks on Right side.(Remove right side space or blanks)

Syntax: RTRIM( string )

SELECT RTRIM('STRING FUNCTION ') returns STRING FUNCTION

REVERSE : Returns reverse of a input string.

Syntax: REVERSE(string)

SELECT REVERSE('STRING FUNCTION') returns NOITCNUF GNIRTS

REPLICATE : Repeats a input string for a specified number of times.

Syntax: REPLICATE (string, integer)

SELECT REPLICATE('FUNCTION', 3) returns FUNCTIONFUNCTIONFUNCTION

SPACE : Returns a string of repeated spaces. The SPACE function is an equivalent of using REPLICATE function to repeat spaces.

Syntax: SPACE ( integer) (If integer is negative, a null string is returned.)

SELECT ('STRING') + SPACE(1) + ('FUNCTION') returns STRING FUNCTION

SUBSTRING : Returns part of a given string.

SUBSTRING function retrieves a portion of the given string starting at the specified character(startindex) to the number of characters specified(length).

Syntax: SUBSTRING (string,startindex,length)

SELECT SUBSTRING('STRING FUNCTION', 1, 6) returns STRING
SELECT SUBSTRING('STRING FUNCTION', 8, 8) returns FUNCTION

DELETE Command

To delete the record fro a table SQL provides a delete statement. General syntax is:-

DELETE FROM <table_name> [WHERE <condition>];

e.g. DELETE FROM student WHERE city = ‘Jammu’;

This command deletes all those records whose city is Jammu.

NOTE: It should be kept in mind that while comparing with the string type values lowercase and uppercase letters are treated as different. That is ‘Jammu’ and ‘jammu’ is different while comparing.

UPDATE Command

To update the data stored in the data base, UOPDATE command is used.

e. g. UPDATE student SET marks = marks + 100;

Increase marks of all the students by 100.

e. g. UPDATE student SET City = ‘Udhampur’ WHERE city = ‘Jammu’;

changes the city of those students to Udhampur whose city is Jammu.

We can also update multiple columns with update command, like

e. g. UPDATE student set marks = marks + 20, city = ‘Jalandhar’

WHERE city NOT IN (‘Jammu’,’Udhampur’);

CREATE VIEW Command

In SQL we can create a view of the already existing table that contains specific attributes of the table.

e. g. the table student that we created contains following fields:

Student (Roll_no, Name, Marks, Class, City)

Suppose we need to create a view v_student that contains Roll_no,name and class of student table, then Create View command can be used:

CREATE VIEW v_student AS SELECT Roll_no, Name, Class FROM student;

The above command create a virtual table (view) named v_student that has three attributes as mentioned and all the rows under those attributes as in student table.

We can also create a view from an existing table based on some specific conditions, like

CREATE VIEW v_student AS SELECT Roll_no, Name, Class FROM student WHERE City <>’Jammu’;

The main difference between a Table and view is that

A Table is a repository of data. The table resides physically in the database.
A View is not a part of the database's physical representation. It is created on a table or another view. It is precompiled, so that data retrieval behaves faster, and also provides a secure accessibility mechanism.

ALTER TABLE Command

In SQL if we ever need to change the structure of the database then ALTER TABLE command is used. By using this command we can add a column in the existing table, delete a column from a table or modify columns in a table.

Adding a column

The syntax to add a column is:-

ALTER TABLE table_name
ADD column_name datatype;

e.g ALTER TABLE student ADD(Address varchar(30));

The above command add a column Address to the table atudent.

If we give command

SELECT * FROM student;

The following data gets displayed on screen:

Roll_no	Name	Class	Marks	City	Address
101	Rohan	XI	400	Jammu
102	Aneeta Chopra	XII	390	Udhampur
103	Pawan Kumar	IX	298	Amritsar
104	Rohan	IX	376	Jammu
105	Sanjay	VII	240	Gurdaspur
113	Anju Mahajan	VIII	432	Pathankot

Note that we have just added a column and there will be no data under this attribute. UPDATE command can be used to supply values / data to this column.

Removing a column

ALTER TABLE table_name
DROP COLUMN column_name;

e.g ALTER TABLE Student
DROP COLUMN Address;

The column Address will be removed from the table student.

DROP TABLE Command

Sometimes you may need to drop a table which is not in use. DROP TABLE command is used to Delete / drop a table permanently. It should be kept in mind that we can not drop a table if it contains records. That is first all the rows of the table have to be deleted and only then the table can be dropped. The general syntax of this command is:-

DROP TABLE <table_name>;

e.g DROP TABLE student;

This command will remove the table student

SECTION B: CONCEPT BASED QUESTIONS

(Very Short Answer questions 1 & 2 Marks)

Q2. Define the terms:

i. Database Abstraction

ii. Data inconsistency

iii. Conceptual level of database implementation/abstraction

iv. Primary Key

v. Candidate Key

vi. Relational Algebra

vii Domain

Ans

i. Database Abstraction

Ans: Database system provides the users only that much information that is required

by them, and hides certain details like, how the data is stored and maintained in

database at hardware level. This concept/process is Database abstraction.

ii. Data inconsistency

Ans: When two or more entries about the same data do not agree i.e. when one of

them stores the updated information and the other does not, it results in data

inconsistency in the database.

iii. Conceptual level of database implementation/abstraction

Ans: It describes what data are actually stored in the database. It also describes the

relationships existing among data. At this level the database is described logically in

terms of simple data-structures.

iv. Primary Key

Ans : It is a key/attribute or a set of attributes that can uniquely identify tuples within the relation.

v. Candidate Key

Ans : All attributes combinations inside a relation that can serve as primary key are candidate key as they are candidates for being as a primary key or a part of it.

vi. Relational Algebra

Ans : It is the collections of rules and operations on relations(tables). The various operations are selection, projection, Cartesian product, union, set difference and intersection, and joining of relations.

vii. Domain

Ans : it is the pool or collection of data from which the actual values appearing in a given column are drawn.

SECTION C: HOTS

Q1 Write SQL commands for (i) to (viii) on the basis of relations given below:

BOOKS

book_id Book_name author_name Publishers Price Type qty

k0001 Let us C Sanjay mukharjee EPB 450 Comp 15

p0001 Genuine J. Mukhi FIRST PUBL. 755 Fiction 24

m0001 Mastering c++ Kanetkar EPB 165 Comp 60

n0002 Vc++ advance P. Purohit TDH 250 Comp 45

k0002 Near to heart Sanjeev FIRST PUBL. 350 Fiction 30

ISSUED

Book_ID	Qty_Issued
L02	13
L04	5
L05	21

i. To show the books of FIRST PUBL Publishers written by P.Purohit.

ii. To display cost of all the books written for FIRST PUBL.

iii. Depreciate the price of all books of EPB publishers by 5%.

iv. To display the BOOK_NAME,price of the books whose more than 3 copies have been issued.

v. To show total cost of books of each type.

vi. To show the detail of the most costly book.

Answers:

Q1.

Ans i: select * from books where publishers=’FIRST PUBL’

Ans ii: select sum(price*qty) from books where publishers=’FIRST PUBL’;

Ansiii: update books set price=price-0.5*price where publishers=’EPB’;

Ans iv: select BOOK_NAME,price from books, issued where

books.book_id=issued.book_id and quantity_issued>3;

Ans v: select sum(price*qty) from books group by type;

Ans vi: select * from books where price=(select max(price) from books));

Q2. Write SQL commands for (a) to (f) and write output for (g) on the basis of PRODUCTS relation given below:

PRODUCT TABLE

PCODE PNAME COMPANY PRICE STOCK MANUFACTURE WARRANTY

P001 TV BPL 10000 200 12-JAN-2008 3

P002 TV SONY 12000 150 23-MAR-2007 4

P003 PC LENOVO 39000 100 09-APR-2008 2

P004 PC COMPAQ 38000 120 20-JUN-2009 2

P005 HANDYCAM SONY 18000 250 23-MAR-2007 3

a) To show details of all PCs with stock more than 110.

b) To list the company which gives warranty for more than 2 years.

c) To find stock value of the BPL company where stock value is sum of the products of price and stock.

d) To show number of products from each company.

e) To count the number of PRODUCTS which shall be out of warranty on 20-NOV-2010.

f) To show the PRODUCT name which are within warranty as on date.

g). Give the output of following statement.

(i) Select COUNT(distinct company) from PRODUCT.

(ii) Select MAX(price)from PRODUCT where WARRANTY<=3

Answers:

Ans a: select * from products where pname=’TV’ and stock>110;

Ans b: select company from products where warranty>2;

Ans c: select sum(price*stock) from PRODUCTS where company=’BPL’;

Ans d: select company,COUNT(*) from products group by company;

Ans e: select count(*) from products where (‘20-NOV-2010’- manufacture)/365>warranty;

Ans f: select pname from products where (sysdate- manufacture)/365<warranty;

Ansg (i): 4

Ans(ii): 39000

Some practice questions from Database and SQL :

2 marks questions

1. What is relation? What is the difference between a tuple and an attribute?

2. Define the following terminologies used in Relational Algebra:

(i) selection (ii) projection (iii) union (iv) Cartesian product

3. What are DDL and DML?

4. Differentiate between primary key and candidate key in a relation?

5. What do you understand by the terms Cardinality and Degree of a relation in relational database?

6. Differentiate between DDL and DML. Mention the 2 commands for each caterogy.

6 marks questions

Table : SchoolBus

Rtno	Area_overed	Capacity	Noofstudents	Distance	Transporter	Charges
1	Vasant kunj	100	120	10	Shivamtravels	100000
2	Hauz Khas	80	80	10	Anand travels	85000
3	Pitampura	60	55	30	Anand travels	60000
4	Rohini	100	90	35	Anand travels	100000
5	Yamuna Vihar	50	60	20	Bhalla Co.	55000
6	Krishna Nagar	70	80	30	Yadav Co.	80000
7	Vasundhara	100	110	20	Yadav Co.	100000
8	Paschim Vihar	40	40	20	Speed travels	55000
9	Saket	120	120	10	Speed travels	100000
10	Jank Puri	100	100	20	Kisan Tours	95000

(b) To show all information of students where capacity is more than the no of student in order of rtno.

(d) To show transporter wise total no. of students traveling.

(e) To show rtno, area_covered and average cost per student for all routes where average cost per student is - charges/noofstudents.

(f) Add a new record with following data:

(11, “ Moti bagh”,35,32,10,” kisan tours “, 35000)

(g) Give the output considering the original relation as given:

(i) select sum(distance) from schoolbus where transporter= “ Yadav travels”;

(ii) select min(noofstudents) from schoolbus;

(iii) select avg(charges) from schoolbus where transporter= “ Anand travels”;

(i) select distinct transporter from schoolbus;

TABLE : GRADUATE

S.NO	NAME	STIPEND	SUBJECT	AVERAGE	DIV.
1	KARAN	400	PHYSICS	68	I
2	DIWAKAR	450	COMP. Sc.	68	I
3	DIVYA	300	CHEMISTRY	62	I
4	REKHA	350	PHYSICS	63	I
5	ARJUN	500	MATHS	70	I
6	SABINA	400	CEHMISTRY	55	II
7	JOHN	250	PHYSICS	64	I
8	ROBERT	450	MATHS	68	I
9	RUBINA	500	COMP. Sc.	62	I
10	VIKAS	400	MATHS	57	II

(a) List the names of those students who have obtained DIV 1 sorted by NAME.

(b) Display a report, listing NAME, STIPEND, SUBJECT and amount of stipend received in a year assuming that the STIPEND is paid every month.

(c) To count the number of students who are either PHYSICS or COMPUTER SC graduates.

(d) To insert a new row in the GRADUATE table: 11,”KAJOL”, 300, “computer sc”, 75, 1

(e) Give the output of following sql statement based on table GRADUATE:

(i) Select MIN(AVERAGE) from GRADUATE where SUBJECT=”PHYSICS”;

(ii) Select SUM(STIPEND) from GRADUATE WHERE div=2;

(iii) Select AVG(STIPEND) from GRADUATE where AVERAGE>=65;

(iv) Select COUNT(distinct SUBDJECT) from GRADUATE;

(f) Assume that there is one more table GUIDE in the database as shown below:

Table: GUIDE

MAINAREA	ADVISOR
PHYSICS	VINOD
COMPUTER SC	ALOK
CHEMISTRY	RAJAN
MATHEMATICS	MAHESH

g) What will be the output of the following query:

SELECT NAME, ADVISOR FROM GRADUATE,GUIDE WHERE SUBJECT= MAINAREA;

3.Write SQL command for (i) to (vii) on the basis of the table SPORTS

Table: SPORTS

Student NO	Class	Name	Game1	Grade	Game2	Grade2
10	7	Sammer	Cricket	B	Swimming	A
11	8	Sujit	Tennis	A	Skating	C
12	7	Kamal	Swimming	B	Football	B
13	7	Venna	Tennis	C	Tennis	A
14	9	Archana	Basketball	A	Cricket	A
15	10	Arpit	Cricket	A	Atheletics	C

(a) Display the names of the students who have grade ‘C’ in either Game1 or Game2 or both.

(b) Display the number of students getting grade ‘A’ in Cricket.

(d) Display the games taken up by the students, whose name starts with ‘A’.

(e) Assign a value 200 for Marks for all those who are getting grade ‘B’ or grade ‘A’ in both Game1 and Game2.

(f) Arrange the whole table in the alphabetical order of Name.

(g) Add a new column named ‘Marks’.

(h)

4. Write SQL command for (i) to (vii) on the basis of the table Employees & EmpSalary

Table: Employees

Empid	Firstname	Lastname	Address	City
010	Ravi	Kumar	Raj nagar	GZB
105	Harry	Waltor	Gandhi nagar	GZB
152	Sam	Tones	33 Elm St.	Paris
215	Sarah	Ackerman	440 U.S. 110	Upton
244	Manila	Sengupta	24 Friends street	New Delhi
300	Robert	Samuel	9 Fifth Cross	Washington
335	Ritu	Tondon	Shastri Nagar	GZB
400	Rachel	Lee	121 Harrison St.	New York
441	Peter	Thompson	11 Red Road	Paris

Table: EmpSalary

Empid	Salary	Benefits	Designation
010	75000	15000	Manager
105	65000	15000	Manager
152	80000	25000	Director
215	75000	12500	Manager
244	50000	12000	Clerk
300	45000	10000	Clerk
335	40000	10000	Clerk
400	32000	7500	Salesman
441	28000	7500	salesman

Write the SQL commands for the following :

(i) To show firstname,lastname,address and city of all employees living in paris.

(ii)To display the content of Employees table in descending order of Firstname.

(iii) To display the firstname,lastname and total salary of all managers from the tables Employee and empsalary , where total salary is calculated as salary+benefits.

(iv) To display the maximum salary among managers and clerks from the table Empsalary.

Give the Output of following SQL commands:

(i) Select firstname,salary from employees ,empsalary where designation = ‘Salesman’ and Employees.empid=Empsalary.empid;

(ii) Select count(distinct designation) from empsalary;

(iii) Select designation, sum(salary) from empsalary group by designation having count(*)>2;

(iv) Select sum(benefits) from empsalary where designation =’Clerk’;

CBSE Computer Science and Informatics Practices

CBSE Computer Science and Informatics Practices

CLASS XII COMPUTER SCIENCE CHAPTER 11 & 12 DATABASE AND SQL

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