Database Management Lab -SQL Queries

Experiment No: 1
Title: Implementation of DDL commands of SQL with suitable examples
 Create table
 Alter table
 Drop Table
Objective:
 To understandthe differentissuesinvolvedinthe designandimplementationof adatabase
system

 To understandand use data definitionlanguagetowrite queryfora database
Theory:
Oracle has many tools such as SQL * PLUS, Oracle Forms, Oracle Report Writer, Oracle
Graphics etc.
 SQL * PLUS: The SQL * PLUS tool is made up of two distinct parts. These are

 Interactive SQL: Interactive SQL is designed for create, access and
manipulate data structures like tables and indexes.

 PL/SQL: PL/SQL can be used to developed programs for different
applications.


 Oracle Forms: This tool allows you to create a data entry screen along with the
suitable menu objects. Thus it is the oracle forms tool that handles data gathering and
data validation in a commercial application.


 Report Writer: Report writer allows programmers to prepare innovative reports
using data from the oracle structures like tables, views etc. It is the report writer tool
that handles the reporting section of commercial application.


 Oracle Graphics: Some of the data can be better represented in the form of pictures.
The oracle graphics tool allows programmers to prepare graphs using data from oracle
structures like tables, views etc.

SQL (Structured Query Language):
Structured Query Language is a database computer language designed for managing data
in relational database management systems (RDBMS), and originally based upon Relational
Algebra. Its scope includes data query and update, schema creation and modification, and
data access control.
SQL was one of the first languages for Edgar F. Codd's relational model and became the
most widely used language for relational databases.
 IBM developed SQL in mid of 1970’s.

 Oracle incorporated in the year 1979.

 SQL used by IBM/DB2 and DS Database Systems.

 SQL adopted as standard language for RDBS by ASNI in 1989.
DATA TYPES:
1. CHAR (Size): This data type is used to store character strings values of fixed length.
The size in brackets determines the number of characters the cell can hold. The
maximum number of character is 255 characters.
2. VARCHAR (Size) / VARCHAR2 (Size): This data type is used to store variable length
alphanumeric data. The maximum character can hold is 2000 character.
3. NUMBER (P, S): The NUMBER data type is used to store number (fixed or floating
point). Number of virtually any magnitude may be stored up to 38 digits of precision.
Number as large as 9.99 * 10
124
. The precision (p) determines the number of places to
the right of the decimal. If scale is omitted then the default is zero. If precision is
omitted, values are stored with their original precision up to the maximum of 38 digits.
4. DATE: This data type is used to represent date and time. The standard format is DD-
MM-YY as in 17-SEP-2009. To enter dates other than the standard format, use the

appropriate functions. Date time stores date in the 24-Hours format. By default the time
in a date field is 12:00:00 am, if no time portion is specified. The default date for a date
field is the first day the current month.
5. LONG: This data type is used to store variable length character strings containing up to
2GB. Long data can be used to store arrays of binary data in ASCII format. LONG
values cannot be indexed, and the normal character functions such as SUBSTR cannot
be applied.
6. RAW: The RAW data type is used to store binary data, such as digitized picture or
image. Data loaded into columns of these data types are stored without any further
conversion. RAW data type can have a maximum length of 255 bytes. LONG RAW
data type can contain up to 2GB.
SQL language is sub-divided into several language elements, including:
 Clauses, which are in some cases optional, constituent components of statements and
queries.

 Expressions, which can produce either scalar values or tables consisting of columns and
rows of data.

 Predicates which specify conditions that can be evaluated to SQL three-valued logic
(3VL) Boolean truth values and which are used to limit the effects of statements and
queries, or to change program flow.

 Queries which retrieve data based on specific criteria.

 Statements which may have a persistent effect on schemas and data, or which may
control transactions, program flow, connections, sessions, or diagnostics.

 SQL statements also include the semicolon (";") statement terminator. Though not
required on every platform, it is defined as a standard part of the SQL grammar.

 Insignificant white space is generally ignored in SQL statements and queries, making it
easier to format SQL code for readability.
There are five types of SQL statements. They are:
1. DATA DEFINITION LANGUAGE (DDL)
2. DATA MANIPULATION LANGUAGE (DML)
3. DATA RETRIEVAL LANGUAGE (DRL)
4. TRANSATIONAL CONTROL LANGUAGE (TCL)
5. DATA CONTROL LANGUAGE (DCL)
1. DATA DEFINITION LANGUAGE (DDL): The Data Definition Language (DDL) is
used to create and destroy databases and database objects. These commands will primarily be
used by database administrators during the setup and removal phases of a database project.
Let's take a look at the structure and usage of four basic DDL commands:
1. CREATE 2. ALTER 3. DROP 4. RENAME
1. CREATE:
(a)CREATE TABLE: This is used to create a new relation (table)
Syntax: CREATE TABLE <relation_name/table_name >
(field_1 data_type(size),field_2 data_type(size), .. . );
Example:
SQL> CREATE TABLE Student (sno NUMBER (3), sname CHAR (10), class CHAR (5));
2. ALTER:
(a)ALTER TABLE ...ADD...: This is used to add some extra fields into existing
relation.

Syntax: ALTER TABLE relation_name ADD (new field_1 data_type(size), new field_2
data_type(size),..);
Example: SQL>ALTER TABLE std ADD (Address CHAR(10));
(b)ALTER TABLE...MODIFY...: This is used to change the width as well as data
type of fields of existing relations.
Syntax: ALTER TABLE relation_name MODIFY (field_1 newdata_type(Size), field_2
newdata_type(Size),....field_newdata_type(Size));
Example:SQL>ALTER TABLE student MODIFY(sname VARCHAR(10),class
VARCHAR(5));
c) ALTER TABLE..DROP...: This is used to remove any field of existing relations.
Syntax: ALTER TABLE relation_name DROP COLUMN (field_name);
Example:SQL>ALTER TABLE student DROP column (sname);
d)ALTER TABLE..RENAME...: This is used to change the name of fields in
existing relations.
Syntax: ALTER TABLE relation_name RENAME COLUMN (OLD field_name) to
(NEW field_name);
Example: SQL>ALTER TABLE student RENAME COLUMN sname to stu_name;
3. DROP TABLE: This is used to delete the structure of a relation. It permanently deletes
the records in the table.
Syntax: DROP TABLE relation_name;
Example: SQL>DROP TABLE std;
4. RENAME: It is used to modify the name of the existing database object.
Syntax: RENAME TABLE old_relation_name TO new_relation_name;
Example: SQL>RENAME TABLE std TO std1;

Experiment No:2
Title : Implementation of DML commands of SQL with suitable examples
 Insert table
 Update table
 Delete Table
Objective :
 To understandthe differentissuesinvolvedinthe designandimplementationof a
database system

 To understandanduse data manipulationlanguage toquery,update,andmanage a
database
Theory :
DATA MANIPULATION LANGUAGE (DML): The Data Manipulation Language
(DML) is used to retrieve, insert and modify database information. These commands will be
used by all database users during the routine operation of the database. Let's take a brief look
at the basic DML commands:
1. INSERT 2. UPDATE 3. DELETE
1. INSERT INTO: This is used to add records into a relation. These are three type of
INSERT INTO queries which are as
a) Inserting a single record
Syntax: INSERT INTO < relation/table name> (field_1,field_2……field_n)VALUES
(data_1,data_2,........data_n);
Example: SQL>INSERT INTO student(sno,sname,class,address)VALUES
(1,’Roki’,’DIU’,’Dhaka’);
b) Inserting a single record
Syntax: INSERT INTO < relation/table name>VALUES (data_1,data_2,........data_n);
Example: SQL>INSERT INTO student VALUES (1,’Roki’,’DIU’,’Dhaka’);
c) Inserting all records from another relation
Syntax: INSERT INTO relation_name_1 SELECT Field_1,field_2,field_n
FROM relation_name_2 WHERE field_x=data;

Example: SQL>INSERT INTO std SELECT sno,sname FROM student
WHERE name = ‘Sakib‘;
d) Inserting multiple records
Syntax: INSERT INTO relation_name field_1,field_2,.....field_n) VALUES
(&data_1,&data_2,........&data_n);
Example: SQL>INSERT INTO student (sno, sname, class,address)
VALUES (&sno,’&sname’,’&class’,’&address’);
Enter value for sno: 101
Enter value for name: Roki
Enter value for class: DIU
Enter value for name: Dhaka
2. UPDATE-SET-WHERE: This is used to update the content of a record in a relation.
Syntax: SQL>UPDATE relation name SET Field_name1=data,field_name2=data,
WHERE field_name=data;
Example: SQL>UPDATE student SET sname = ‘ali’ WHERE sno=1;
3. DELETE-FROM: This is used to delete all the records of a relation but it will retain the
structure of that relation.
a) DELETE-FROM: This is used to delete all the records of relation.
Syntax:SQL>DELETE FROM relation_name;
Example: SQL>DELETE FROM std;
b) DELETE -FROM-WHERE: This is used to delete a selected record from a relation.
Syntax: SQL>DELETE FROM relation_name WHERE condition;
Example: SQL>DELETE FROM student WHERE sno = 2;

Experiment No: 3

 Aggregate Function
Aggregative operators: In addition to simply retrieving data, we often want to perform some
computation or summarization. SQL allows the use of arithmetic expressions. We now
consider a powerful class of constructs for computing aggregate values such as MIN and
SUM.
1. Count: COUNT following by a column name returns the count of tuple in that column. If
DISTINCT keyword is used then it will return only the count of unique tuple in the column.
Otherwise, it will return count of all the tuples (including duplicates) count (*) indicates all
the tuples of the column.
Syntax: COUNT (Column name)
Example: SELECT COUNT (Sal) FROM emp;
2. SUM: SUM followed by a column name returns the sum of all the values in that
column. Syntax: SUM (Column name)
Example: SELECT SUM (Sal) From emp;
3. AVG: AVG followed by a column name returns the average value of that column
values. Syntax: AVG (n1, n2...)
Example: Select AVG (10, 15, 30) FROM DUAL;
4. MAX: MAX followed by a column name returns the maximum value of that
column. Syntax: MAX (Column name)
Example: SELECT MAX (Sal) FROM emp;
SQL> select deptno, max(sal) from emp group by deptno;
DEPTNO MAX (SAL)
------ --------
10 5000
20 3000
30 2850

SQL> select deptno, max (sal) from emp group by deptno having max(sal)<3000;
DEPTNO MAX(SAL)
----- --------
302850
5. MIN: MIN followed by column name returns the minimum value of that
column. Syntax: MIN (Column name)
Example: SELECT MIN (Sal) FROM emp;
SQL>select deptno,min(sal) from emp group by deptno having min(sal)>1000;
DEPTNO MIN (SAL)
----- --------
101300

Experiment No: 4
Title : Study & Implementation of
 Group by & Having Clause

 Order by Clause

 Indexing
Objective:
To learn the concept of group functions
Theory:
 GROUP BY: This query is used to group to all the records in a relation together for each
and every value of a specific key(s) and then display them for a selected set of fields the
relation.
Syntax: SELECT <set of fields> FROM <relation_name>
GROUP BY <field_name>;
Example: SQL> SELECT EMPNO, SUM (SALARY) FROM EMP GROUP BY
EMPNO;
GROUP BY-HAVING : The HAVING clause was added to SQL because the WHERE
keyword could not be used with aggregate functions. The HAVING clause must follow
the GROUP BY clause in a query and must also precede the ORDER BY clause if used.
Syntax: SELECT column_name, aggregate_function(column_name) FROM table_name
WHERE column_name operator value
GROUP BY column_name
HAVING aggregate_function(column_name) operator value;

Example : SELECT Employees.LastName, COUNT(Orders.OrderID) AS
NumberOfOrders FROM (Orders
INNER JOIN Employees
ON Orders.EmployeeID=Employees.EmployeeID) GROUP BY
LastName HAVING COUNT (Orders.OrderID) > 10;
JOIN using GROUP BY: This query is used to display a set of fields from two relations by
matching a common field in them and also group the corresponding records for each and
every value of a specified key(s) while displaying.
Syntax: SELECT <set of fields (from both relations)> FROM relation_1,relation_2
WHERE relation_1.field_x=relation_2.field_y GROUP BY field_z;
Example:
SQL> SELECT empno,SUM(SALARY) FROM emp,dept
WHERE emp.deptno =20 GROUP BY empno;
 ORDER BY: This query is used to display a selected set of fields from a relation in an
ordered manner base on some field.
Syntax: SELECT <set of fields> FROM <relation_name>
ORDER BY <field_name>;
Example: SQL> SELECT empno, ename, job FROM emp ORDER BY job;
JOIN using ORDER BY: This query is used to display a set of fields from two relations by
matching a common field in them in an ordered manner based on some fields.
Syntax: SELECT <set of fields (from both relations)> FROM relation_1, relation_2
WHERE relation_1.field_x = relation_2.field_y ORDER BY field_z;
Example: SQL> SELECT empno,ename,job,dname FROM emp,dept
WHERE emp.deptno = 20 ORDER BY job;

 INDEXING: An index is an ordered set of pointers to the data in a table. It is based on
the data values in one or more columns of the table. SQL Base stores indexes separately
from tables.

An index provides two benefits:

 It improves performance because it makes data access faster.

 It ensures uniqueness. A table with a unique index cannot have two rows
with the same values in the column or columns that form the index key.
Syntax:
CREATE INDEX <index_name> on <table_name> (attrib1,attrib 2….attrib n);
Example:
CREATE INDEX id1 on emp(empno,dept_no);

Experiment No: 5
Title : Study & Implementation of
 Views
VIEW: In SQL, a view is a virtual table based on the result-set of an SQL statement.
A view contains rows and columns, just like a real table. The fields in a view are fields
from one or more real tables in the database.
You can add SQL functions, WHERE, and JOIN statements to a view and present the
data as if the data were coming from one single table.
A view is a virtual table, which consists of a set of columns from one or more tables. It is
similar to a table but it does not store in the database. View is a query stored as an object.
Syntax: CREATE VIEW <view_name> AS SELECT <set of
fields> FROM relation_name WHERE (Condition)
Example:
SQL> CREATE VIEW employee AS SELECT empno,ename,job
FROM EMP WHERE job = ‘clerk’;
SQL> View created.
Example:
CREATE VIEW [Current Product List] AS
SELECT ProductID, ProductName
FROM Products
WHERE Discontinued=No;
UPDATING A VIEW : A view can updated by using the following syntax :
Syntax : CREATE OR REPLACE VIEW view_name
AS SELECT column_name(s)
FROM table_name
WHERE condition
DROPPING A VIEW: A view can deleted with the DROP VIEW command.
Syntax: DROP VIEW <view_name> ;

Experiment No: 6
NOT NULL: When a column is defined as NOTNULL, then that column becomes a
mandatory column. It implies that a value must be entered into the column if the record is to
be accepted for storage in the table.
Syntax:
CREATE TABLE Table_Name (column_name data_type (size) NOT NULL, );
Example:
CREATE TABLE student (sno NUMBER(3)NOT NULL, name CHAR(10));
PRIMARY KEY: A field which is used to identify a record uniquely. A column or
combination of columns can be created as primary key, which can be used as a reference
from other tables. A table contains primary key is known as Master Table.
 It must uniquely identify each record in a table.

 It must contain unique values.

 It cannot be a null field.

 It cannot be multi port field.

 It should contain a minimum no. of fields necessary to be called unique.
Syntax:
CREATE TABLE Table_Name(column_name data_type(size) PRIMARY KEY,
….);
Example:
CREATE TABLE faculty (fcode NUMBER(3) PRIMARY KEY, fname
CHAR(10));
FOREIGN KEY: It is a table level constraint. We cannot add this at column level. To
reference any primary key column from other table this constraint can be used. The table in
which the foreign key is defined is called a detail table. The table that defines the primary
key and is referenced by the foreign key is called the master table.
Syntax: CREATE TABLE Table_Name(column_name data_type(size)
FOREIGN KEY(column_name) REFERENCES table_name);
Example:
CREATE TABLE subject (scode NUMBER (3) PRIMARY KEY, subname
CHAR(10),fcode NUMBER(3), FOREIGN KEY(fcode) REFERENCE faculty );

Defining integrity constraints in the alter table command:
Syntax: ALTER TABLE Table_Name ADD PRIMARY KEY (column_name);
Example: ALTER TABLE student ADD PRIMARY KEY (sno);
(Or)
Syntax: ALTER TABLE table_name ADD CONSTRAINT constraint_name
PRIMARY KEY(colname)
Example: ALTER TABLE student ADD CONSTRAINT SN PRIMARY KEY(SNO)
Dropping integrity constraints in the alter table command:
Syntax: ALTER TABLE Table_Name DROP constraint_name;
Example: ALTER TABLE student DROP PRIMARY KEY;
(or)
Syntax: ALTER TABLE student DROP CONSTRAINT constraint_name;
Example: ALTER TABLE student DROP CONSTRAINT SN;

Database Management Lab -SQL Queries

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