Download Relational Database Mgmt.System

What is DBMS ?
A
collection of interrelated and persistent data
 Goal of DBMS is to provide an environment to
Retrieve and Store data
 Designed to Manage Large Bodies of
Information. This involves
–
–
–
–
Data Modeling
Query Processing
Security
Concurrency control
Types of Database Systems
 Relational


Data and relationships are represented by a collection of tables
Each table has a no. of columns with unique names
 Network



Database Management System
Database System
Data are represented by collections of records
Relationships among data are represented by links
Organization is that of an arbitrary graph
 Hierarchical


Database System
Similar to Network model
Organization of the records is as a collection of trees, rather than arbitrary graph
Codd’s Rules
The most popular data storage model is the relational database,
which grew from the seminal paper "A Relational Model of Data
for Large Shared Data Banks," written by Dr. E. F. Codd in 1970.
SQL evolved to service the concepts of the relational database
model. Dr. Codd defined 13 rules, oddly enough referred to as
Codd's 12 Rules, for the relational model:
0. A relational DBMS must be able to manage databases
entirely through its relational capabilities.
1. Information rule-- All information in a relational
database (including table and column names) is
represented explicitly as values in tables.
Codd’s Rules...
2. Guaranteed access--Every value in a relational database is
guaranteed to be accessible by using a combination of the table
name, primary key value, and column name.
3. Systematic null value support--The RDBMS provides
systematic support for the treatment of null values (unknown or
inapplicable data), distinct from default values, and independent
of any domain.
4. Active, online relational catalog--The description of the
database and its contents is represented at the logical level as
tables and can therefore be queried using the database language.
Codd’s Rules...
5. Comprehensive data sublanguage--At least one
supported language must have a well-defined syntax and
be comprehensive. It must support data definition,
manipulation, integrity rules, authorization, and transactions
7. Set-level insertion, update, and deletion--The
RDBMS supports not only set-level retrievals but also setlevel inserts, updates, and deletes.
8. Physical data independence--Application programs
and ad hoc programs are logically unaffected when physical
access methods or storage structures are altered.
Codd’s Rules...
9. Logical data independence--Application programs
and ad hoc programs are logically unaffected, to the extent
possible, when changes are made to the table structures.
10. Integrity independence--The database language
must be capable of defining integrity rules. They must be
stored in the online catalog, and they cannot be bypassed.
11. Distribution independence--Application programs
and ad hoc requests are logically unaffected when data is
first distributed or when it is redistributed.
12. Nonsubversion--It must not be possible to bypass
the integrity rules defined through the database language
by using lower-level languages.
RDBMS
A
relational database is a collection of
relations or two-dimensional tables
 Manipulate relational databases a set at a
time rather than a record at a time.

Eg. Select all employees who work in department 30
Advantages of RDBMS
 Redundancy
can be reduced
 Inconsistency can be avoided
 Data can be shared
 Standards can be enforced
 Integrity can be maintained
 Concurrency can be controlled
DBMS vs. RDBMS

DBMS
 No relationship between
the tables
 No transaction control
support e.g. COMMIT &
ROLLBACK
 No Crashrecovery on
database crash

RDBMS
 Relationship between
tables supported
 Transactions can be
controlled easily
 Crashrecovery possible
on database crash
Entity Relationship Modelling
 Identify
the basic entities in a business
scenario to capture important data
 Read and explain an Entity-Relationship
diagram that captures business data
 List and define basic kinds of data
relationships
 Define normalization and explain it’s benefits
Entity Relationship Model
EMPLOYEE
DEPARTMENT
#*NUMBER
*first name
*last name
*hire date
o salary
o job
#*number
Assigned to
Responsible for
*name
*location
Advantages of E-R Model
E-R model documents an organization’s
information requirements in a clear and
precise manner
 User’s can easily understand the pictorial form
of an E-R model
 An E-R model can be easily developed and
refined
 It provides an effective framework for
integrating multiple applications.
 An
Find Categories of Data
 In
an effective business system, data are divided
into discrete categories or entities.An entity is a
“thing of significance” about which information
needs to be known.
 Attributes describe entities and hold the specific
pieces of information that need to be known about
the entity.
Entity Diagram
 Entity
diagrams provide a formal,concise
means for recording information about entities
 Entities are always shown UPPER case.
 eg.
EMPLOYEE
#*number
*first name
*last name
o job
DEPARTMENT
#* number
*name
*location
Kinds of Relationships
 One
to One Relationships
 Many
to One Relationships
 Many
to Many relationships
Denotes optional
relationship
One to One Relationship
It has a degree of one and only one in both directions
MICROCOMPUTER
The host for
Incorporated
into
MOTHERBOARD
Each MICROCOMPUTER must be the host for one and
only one MOTHERBOARD
Each MOTHERBOARD may be incorporated into one and
only one MICROCOMPUTER
Many to one Relationship
It has a degree of one or more in one direction and one
and only one in the other direction
ORDER
Given by
May give
CUSTOMER
Each ORDER must be given by one and only one CUSTOMER
Each CUSTOMER may give one or more ORDERs
Many to Many Relationship
It has a degree of one or more in both directions
ORDER
Have
Allocated to
ITEM
Each ORDER may HAVE one or more ITEMs
Each ITEM may be allocated to one or more ORDERs
Attributes
 Attributes
are information about an entity that
needs to be known or held
 Attributes describe an entity by qualifying
,identifying,classifying,quantifying or expressing
the state of the entity
 Attributes are always represented in LOWER case
in an E-R diagram
Attribute- Examples
EMPLOYEE
COURSE
code
code
first name
name
last name
duration
hiredate
fee
salary
hiredate
Attribute - Facts
 Each
attribute should have a single value for each
entity instance.A repeated attribute indicates a
missing entity
 An attribute should not be derived or calculated
from the existing values of other attributes eg
(totals,counts etc.). Do not include derived
attributes in an E-R model as derived attributes are
redundant.
Types of Attributes
Identify each attribute’s optionality using an attribute tag

Mandatory Attributes


A value must be known for each entity occurrence
The attribute name is tagged with *
Optional Attributes
A value maybe known for each entity occurrence
•
The attribute name is tagged with o
Assign Unique Identifier
A unique identifier (UID) is any combination of
attributes and/or relationships that serve to
uniquely identify an occurrence of an
entity.Each entity occurrence must be uniquely
identifiable
eg.
DEPARTMENT
#*number
*name
The UID for the entity DEPARTMENT is the attribute number
Facts about UID
 An
entity must have a UID or it is not an entity
 An entity may have more than one UID.In this case
select one candidate UID to be the primary UID
and the others to be secondary UIDs.
Integrity Rules
 Define
primary keys and foreign keys
 Protect data integrity
 Translate any ER-data model into a relational
database design
Integrity Constraints
 PRIMARY
KEY
 FOREIGN KEY
 UNIQUE
 NOT NULL
 CHECK
Primary Key





A primary key is a column or a set of columns that uniquely
identifies each row in a table.
Each table must have a primary key and the primary key must me
unique.
No part of the primary key may be null ie. no part of a primary key
may lack a value.
A primary key consisting of multiple columns is called a
composite primary key or a compound key.
A table can have several candidate keys.A candidate key is a
column or a combination of columns that can serve as the
primary key for the table where both should be independently
unique and not null.
Primary Key- Examples
Composite primary key
Bank No. Account No. Balance
Date_opened
104
75760
12,000.50
21-OCT-89
105
77956
100.10
103
89570
55,775.00
15-JAN-85
105
55890
15,001.90
25-SEP-91
The columns of a composite primary key must be
unique in combination,although individual columns can
have duplicate values.
Primary Key - Examples
Primary key
Alternate key
Id.
Name
Dept_Id
Payroll_id
1
Scott
50
9710
2
Martin
30
8730
3
Michael
50
1157
4
George
40
3394
All candidate keys must be unique and NOT NULL individually
Foreign Keys





A foreign key is a column or a set of columns in one
table that refers to a primary key in the same table or
another table
They are used to combine information from different
tables
They are purely logical and not physical pointers as
they depend on data values
A foreign key value must match an existing primary key
value (or else be NULL)
A foreign key that is a part of a primary key cannot be
NULL,since no part of the primary key can be null
Foreign Key - Examples
Primary key
Foreign key
Dept_Id
EMPLOYEE
E Id
Name
Payroll_id
1
Scott
50
9710
2
Martin
30
8730
3
Michael
50
1157
4
George
40
3394
D Id
Name
30
Finance
DEPARTMENT
Table
40
Sales
50
Operations
Table
EXAMPLE OF CONSTRAINTS
CREATE TABLE emp(
id number(5) CONSTRAINT emp_key_pk PRIMARY KEY,
name varchar2(15) NOT NULL CONSTRAINT
dept_key_unq UNIQUE,
salary number(11,2),
commission_pct number(4,2) CONSTRAINT
emp_comm_pct_check
CHECK(commission_pct IN (10,12.5.15)),
dept_id number(7) CONSTRAINT emp_fk_dept_id
REFERENCES dept(id));
ORACLE DATATYPES
CHAR : Fixed length character value of sizes 1-255
VARCHAR2: Variable length character value of sizes 12000
VARCHAR:Same as varchar2 datatype
LONG: Similar to varchar2 but max. size is 2GB
DATE:Date and time value between Jan 1,4172B.C and
Dec. 31,4712 A.D
NUMBER(p,s):Number value having a max. precision of
p and a maximum scale of s
•the precision is the no. of decimal digits
•the scale is the no. of digits to the right of the
decimal point
DDL AND LOGICAL SCHEMA
OBJECTIVES
 Create
storage structures(tables) to store data
 Modify the structure of an existing table
 Enforce business data integrity by adding and
removing constraints
 Dropping tables
CREATING TABLES
 Produce
a data model that includes entities
,attributes and relationships during the analysis
stage of system development
 Document tables,columns,data constraints and
sample data with table instance charts(E-R
model)
CREATE TABLE
SYNTAX
CREATE TABLE [user.] table_name
({column_name datatype | table constraint},
{column_name datatype | table constraint}……)
EXPAMPLE
CREATE TABLE dept
(id number(5) CONSTRAINT dept_key_pk
PRIMARY KEY,
name varchar2(15) NOT NULL CONSTRAINT
dept_key_unq UNIQUE,
location varchar2(15));
Example (CONT’D)
Now create a child table(EMP) based on the master
table DEPT by enforcing a foreign key
CREATE TABLE emp
(id NUMBER(10) CONSTRAINT emp_key_pk PRIMARY KEY,
name VARCHAR2(30) NOT NULL,
salary number(11,2),……..,
dept_id NUMBER(5) CONSTRAINT emp_key_fk_id
REFERENCES dept(id)
);
VERIFYING THE STRUCTURE OF AN OBJECT
SYNTAX
DESC object_name;
DROPPING AN OBJECT
SYNTAX
DROP object_type object_name;
ADD A COLUMN TO A TABLE
SYNTAX
ALTER TABLE table_name
ADD(column_name datatype [,column_name
datatype]………)
EXAMPLE
ALTER TABLE emp
ADD(comments VARCHAR2(155));
MODIFY A COLUMN
SYNTAX
ALTER TABLE table_name
MODIFY(column_name datatype [,column_name
datatype]………)
EXAMPLE
ALTER TABLE emp
MODIFY(salary NOT NULL);
MANIPULATE DATA IN ORACLE TABLES
OBJECTIVES
 Insert
data into a table
 Update existing data in a table
 Delete data from a table
 Select data from a table
INSERT DATA
SYNTAX
INSERT INTO table_name
[(column1,column2……….) ]
VALUES(value1,value2,………..)
EXAMPLE
INSERT INTO dept (id,name,location)
VALUES(60,’PRODUCTION’,’DALLAS’);
UPDATE DATA
SYNTAX
UPDATE table_name
SET column1=value,column2=value………
[WHERE condition]
If where clause is not given then all the rows will be updated
EXAMPLE
UPDATE emp
SET dept_id=20,salary=3450
where id=4156;
DELETE ROWS
SYNTAX
DELETE FROM table_name
[WHERE condition]
EXAMPLE
DELETE FROM dept
where id=70;
SELECT STATEMENT
Present columns from a database table by listing them in the
SELECT clause of the SELECT statement
SELECT… : The columns ,expressions or constants to retrieve
FROM…
: The table from which to retrieve data
WHERE… : The rows to retrieve according to criteria
ORDER BY… : The sort order by which to display rows
DISPLAY ROWS
Display specific rows from a table according to a search
condition with the WHERE clause
SYNTAX
SELECT {*|column name [,column name….]}
FROM table_name
WHERE condition
EXAMPLE
SELECT * FROM emp
WHERE dept_id=10;
PROCESS TRANSACTIONS


The COMMIT statement makes permanent all the changes
performed in the current transaction,tat is , all changes
made to the database since last commit
The ROLLBACK statement makes the work done in the
current transaction undone
ADD AND REMOVE DATA CONSTRAINTS
EXAMPLE
Add a constraint to emp table indicating that a manager
must already exist as a valid employee in the emp table
ALTER TABLE EMP
ADD CONSTRAINT emp_fk_manager_id
FOREIGN KEY (manager_id) REFERENCES emp(id);
ALTER TABLE emp
DROP CONSTRAINT emp_fk_manager_id;
SEQUENCES
•Sequences generate integer values which are
unique
•It is useful for on line transactions where all
clients use a centralized sequence eg. Railway
booking counters
•Can be used for generating primary key
values.
Sequences (CONT’D)
SYNTAX
CREATE SEQUENCE sequence_name
[START WITH n]
[INCREMENT BY m]
[{MAXVALUE o | NOMAXVALUE}]
[{CACHE p | NOCACHE}]
EXAMPLE
CREATE SEQUENCE dept_id
START WITH 10
INCREMENT BY 5
NOCACHE;
Sequences ( CONT’D)
Reference sequences in INSERT commands to generate
unique integer values automatically
Sequence_name.NEXTVAL: returns the next available value
of sequence
Sequence_name.CURRVAL: returns the last value of the
sequence obtained by the current user with
sequence_name.NEXTVAL.It is undefined for any user
session until the user references sequence_name.NEXTVAL
at least once
USERS & SECURITY
OBJECTIVES
 Control
user access to Oracle Server
 Provide access to database
objects(Tables,Views ,Synonyms)
 Confirm access to database objects
 Create synonyms for database objects
 Remove access to database objects from users
PRIVILEGES
 SYSTEM
PRIVILEGES (Managed by DBA)
 OBJECT PRIVILEGES



used by the user to provide access to his/her data objects with SQL
command GRANT
Object privileges include alter,delete,index,insert,references,select,
update
PRIVILEGES (CONT’D)
GRANT
SYNTAX
GRANT [privilege , privilege…..|ALL]
ON object_name
TO [user1_name, user1_name…..|PUBLIC]
[WITH GRANT OPTION]
EXAMPLE
GRANT SELECT,INSERT
ON emp
TO xyz;
PRIVILEGES(CONT’D)
REVOKE
SYNTAX
REVOKE [privilege , privilege….]
ON object_name
FROM [user1_name, user1_name…..|PUBLIC]
[CASCADE CONSTRAINTS]
EXAMPLE
REVOKE SELECT,INSERT
On emp
FROM xyz;
VIEWS
•Logically represent subsets of data from one or more
tables.
•A view does not actually contain data;all data is
derived from the underlying table(s)
•Useful for security and convenience
SYNTAX
CREATE OR REPLACE VIEW view_name [(alias, [alias]
…..) AS [query]
EXAMPLE
Views(CONT’D)
CREATE OR REPLACE VIEW empview
AS SELECT id,last_name,salary
FROM emp
where dept_id=10;
SELECT * FROM empview;
For further security reasons the column headings can be controlled by
including column aliases within the defining SELECT statement
CREATE OR REPLACE VIEW empview
AS SELECT id,first_name ||’’||last_name NAME,
FROM emp;
INDEXES
 Used primarily to speed up the process of data retrieval
 The index should be created on a column having the most unique
values or the column which is frequently included the the WHERE
clause of the SELECT statement.
 Index is automatically created on the column having the
PRIMARY KEY constraint.
 They are automatically updated when the corresponding column
is updated and are dropped when the table is dropped.
 They can be enabled or disabled explicitly as per the
requirements .eg. In case of online processing they can be
disabled explicitly
Indexes(CONT’D)
SYNTAX
CREATE INDEX index_name
ON table_name(column [,column] …);
EXAMPLE
CREATE INDEX emp_index
ON emp(hiredate);
Synonyms(CONT’D)
SYNTAX
CREATE [PUBLIC] SYNONYM synonym_name
FOR table_name;
EXAMPLE
CREATE PUBLIC SYNONYM emp_synonym
FOR emp;
COMPARISION BETWEEN VIEWS
AND SYNONYMS

VIEWS



They can be based on one
or more tables
They are stored objects like
tables having a definite
structure
Users can access views
depending on the Grants
given by the owner of the
view

SYNONYMS



They are based on only one
table
They are only canonical names
and have no definite structure
Users access is limited at the
creation time.
New Features of Oracle8
•Table Partitions
•Object Oriented Features
–Define Objects
–Define Methods
–Support polymorphism
–Support inheritance
DISTRIBUTED DATABASES
•A distributed system is one in which both data and transaction
processing are divided between one or more computers connected
by a network, each computer playing a specific role in the system.
•Replication (insuring that the data at all sites in a distributed
system reflects any changes made anywhere in the system)
•A distributed database is a set of databases stored on multiple
computers that typically appears to applications as a single
database. Consequently, an application can simultaneously
access and modify the data in several databases in a network
Overview of SQL
A
Brief History of SQL
•
SQL was first developed in an IBM laboratory in San Jose,
California, in the late 1970s. The initials stand for Structured
Query Language, and the language itself is often referred to as
"sequel.”
 Features
of SQL
•
English like language.
•
Non-Procedural language.
•
Equally used by end users, developer as well as by
administrators.
Introduction to SQL *Plus
 SQL
*Plus is an Oracle product that supports
ANSI-SQL. It acts as a host to SQL commands,
additionally it supports
•
•
•
•
Procedural option of Oracle (PL/SQL)
Buffer Commands
Script file Commands
Formatting commands
 Starting
•
•
SQL *Plus.
Double click on SQL*Plus icon and then key in the username,
password and the host string.
Username is the name provided DBA, a valid ID to login to the
Guidelines for writing SQL
Commands.
•
•
•
•
•
•
•
•
 SQL
•
•
•
An SQL command is entered at the SQL*Plus prompt and the
subsequent lines are numbered.
Word delimiter is space or tab.
Command entry can be in upper case or lower case.
Command be of SQL, SQL *Plus or PL/SQL
SQL commands may be one line or several lines.
Command words cannot be split across lines.
Most recent SQL or PL/SQL command is stored in SQL Buffer.
Buffer command can be edited or re-executed.
Command Entry.
SQL commands can be terminated by a semicolon, slash (/) or blank
line
Commands terminated by a semicolon or a slash are stored in SQL
buffer and executed.
Commands terminated by a blank line are stored in SQL buffer, but not
DESCRIBE
 Display
the structure of the Table, View or
Synonym.
SQL> describe dept
Name
Null?
Type
------------------------------- -------- ---DEPTNO
NOT NULL
NUMBER(2)
DNAME
VARCHAR2(14)
LOC
VARCHAR2(13)
SQL> desc emp
Name
Null?
Type
------------------------------- -------- ---EMPNO
NOT NULL
NUMBER(4)
ENAME
VARCHAR2(10)
JOB
SELECT Statement
 Used
to retrieve data stored in database tables and
views.
SELECT { * | column_name [, column_name …] }
FROM Table_name
SQL> select * from dept;
DEPTNO
--------10
20
30
40
DNAME
-------------ACCOUNTING
RESEARCH
SALES
OPERATIONS
LOC
------------NEW YORK
DALLAS
CHICAGO
BOSTON
SQL> select empno,ename,job from emp;
Column Aliases in SELECT
Statement.
 Used
from giving meaning full name to the column
heading. By default alias headings cannot contain
blank spaces, unless the alias is enclosed in
double quotes (“ “)
SQL> SELECT ename Employee, sal Salary FROM
Emp;
EMPLOYEE
SALARY
---------- --------KING
5000
BLAKE
2850
CLARK
2450
JONES
2975
MARTIN
1250
ALLEN
1600
TURNER
1500
JAMES
950
WARD
1250
Arithmetic Expression in
SELECT statement.
 An
expression is a combination of one or more
variables, literal /constants, operators and
functions that evaluates to value.
 An expression may contain column names, literal
and the following arithmetic operators.
+(addition), - (Subtraction) , * (Multiplication)
/ (Division), % (Modulus)
SQL> SELECT ename, sal * 12 "Annual Salary"
FROM Emp;
ENAME
Annual Salary
---------- ------------KING
60000
BLAKE
34200
CLARK
29400
Concatenation Operator
 Concatenation
operator (||) is used to link columns
to other columns, arithmetic expressions or literal
to create a character expression.
 Columns on either side of the operator are
combined to make one single column.
SQL> SELECT custid "Customer Id", address||',
'||city "Address"
FROM Customer;
Customer Id Address
----------- ------------------------------------------------------------------100 345 VIEWRIDGE, BELMONT
101 490 BOLI RD., REDWOOD CITY
102 9722 HAMILTON, BURLINGAME
103 HILLVIEW MALL, BURLINGAME
104 574 SURRY RD., CUPERTINO
Handling Null values
 A row
may have a specific column containing no
values, such a column is said to have NULL value.
 A null value is not equal to zero or space character.
 A null value occupies 1 byte of space in storage.
 If column taking part in an expression contains
NULL, result of that expression evaluates to NULL.
For example, when ever COMM column contains
null, the expression (sal * 12 ) + comm results in
NULL.
SQL> SELECT ename, sal * 12, comm, (sal * 12)
+ comm FROM Emp;
ENAME
SAL*12
COMM (SAL*12)+COMM
Continue..
 NVL
function provides facilities to handle NULL
values.
SQL> SELECT ename, sal * 12, comm, (sal * 12)
+ NVL(comm,0) FROM Emp;
ENAME
SAL*12
COMM
(SAL*12)+NVL(COMM,0)
---------- --------- --------- ------------------KING
60000
60000
BLAKE
34200
34200
CLARK
29400
29400
JONES
35700
35700
MARTIN
15000
1400
16400
ALLEN
19200
300
19500
DISTINCT Clause.
 Using
‘DISTINCT’ clause we can eliminate
duplicate rows.
For example, try and see the output of the following
queries.
SQL> SELECT deptno FROM Emp;
DEPTNO
--------10
30
10
20
30
30
30
Sorting Query Results
 By
specifying ORDER BY, the data results are
presented in a sorted order.
 The ordering can be done in ascending or in
descending order. Default is ascending.
 Order by clause must be the last clause in the
SELECT statement.
While ordering in ascending order
•
•
•
•
NULL values appear at the end.
Numeric values appear with the lowest values first.
Date values appear starting from the earliest date.
Character values appear alphabetically. (Capital letters first then small
letters)
SQL> SELECT empno, hiredate FROM emp ORDER BY
hiredate;
Sorting Result on Multiple
Columns
 When
multiple columns are specified, the rows are
sorted according to the values of the first column.
Rows with repeating values for the first column are
then sorted on the second column and so on.
 For
example, to display the names of the
employees in descending order within every job in
ascending order, the query will be
SQL> SELECT job, ename FROM Emp ORDER by job,
ename DESC;
JOB
ENAME
--------- ---------ANALYST
SCOTT
Summary.
 SQL
is the language used by RDBMS to
enable users to access data.
 SQL *Plus is an Oracle product which
supports ANSI-SQL.
 Using DESCRIBE (in short DESC) we can
see the structure of the tables in the
database.
 SELECT statement is used to retrieve data
from the tables, the full syntax is
WHERE Clause
 For
your queries to be more selective you should
use WHERE clause.
 The condition specified with the WHERE clause
acts as a filter and returns only those rows that
satisfy the condition.
Syntax
SELECT … FROM.. WHERE condition(s).
For example, to display details of all employees from
Emp table who are working as salesman. The
Continue..
Comparison operators are categorized as
 Logical Operator
 SQL Operator
 Logical
Operators.
Following is the table of Logical operators.
Operator
=
>
>=
<
<=
!= , <>
SQL>
Meaning
Equal to
Greater than
Greater than or equal to
Less than
Less than or equal to
Not Equal to
SELECT ename, sal FROM Emp WHERE sal <
Continue...
 Constants
used in the WHERE clause can be
compared with valid Oracle column types
 Character and Date constants must be enclosed in
single quotation.
For Example, to display information of employees
joined after ‘15-Dec-1982’, the query is
SQL> SELECT ename, hiredate FROM Emp WHERE
hiredate > '15-DEC-82';
ENAME
HIREDATE
---------- --------ADAMS
12-JAN-83
SQL Operator
 Following
are the four SQL Operators
Operator
Meaning
Between .. AND..
IN (list of values)
LIKE
IS NULL
Between lower value and upper
value, both inclusive
Matching any of a list of values
Matching any of a list of values
is a null value
Between .. AND .. Operator.
 Between
is used in such situations where you
required to retrieve data that lies within a range of
values.
 Both the values (lower and upper) are inclusive.
For example, to see the employees whose date of
IN Operator
 Used
to retrieve data based on a given list of
values.
 IN operator is much efficient that OR operator
(which is Covered later)
Consider a situation in which you need to retrieve the
names of all employees who works as Analyst or
Salesman. The following query would do.
SQL> SELECT ename, job FROM
IN ('ANALYST','SALESMAN')
ENAME
---------MARTIN
ALLEN
JOB
--------SALESMAN
SALESMAN
Emp WHERE job
LIKE operator
 Used
to retrieve similar data from table by
matching a portion of a data with a specific value
 For
matching a portion of a data we use wild char
characters. The following list the wild card
characters and the meaning.
Wildcard
%
_
 For
Meaning
Matches any number of characters
Matches any one character
example, to retrieve data of employees whose
name start with ‘S’, you can use following query.
IS NULL operator
 To
check whether the value is NUL, neither IN
operator nor not the equality operator can be
used. For that IS NULL operator is required.
 E.g
To check out employees who did not earn any
commission, use the following query.
SQL> SELECT ename FROM Emp WHERE comm IS
NULL;
ENAME
---------KING
BLAKE
CLARK
JONES
JAMES
NOT operator

NOT is used to negate a condition.
 They
are used with all Logical operators and SQL
Operators, like
NOT =
Same as <>, !=
NOT <=
Same as >
NOT >
Same as <=
NOT BETWEEN Not between the range
NOT IN
Not in the list
NOT LIKE Not matching the pattern
IS NOT NULL
is not a null value
Compound conditions
 AND
and OR operators may be used to make
compound logical expressions
 AND predicate expects both condition to be TURE
 OR predicate expects either condition to be TURE
For example, to find all salesmen who earn 1250,
the query would be:
SQL> SELECT empno, ename, job, sal FROM Emp
WHERE sal = 1250 AND job = 'SALESMAN';
EMPNO
--------7654
7521
ENAME
---------MARTIN
WARD
JOB
SAL
--------- --------SALESMAN
1250
SALESMAN
1250
Summary
 WHERE
clause in used to select only the
required rows.
 Comparison
operators are categorized to
Logical Operators and Sql operators.
 Logical
 SQL
operators are =, >, <, >=, <=, !=, <>
operators are BETWEEN…AND.., IN,
Functions.
 Functions
are used to manipulate data and
summarize query results. You can pass one or
more arguments to functions. They will return only
one value as a result.
 Arguments are passed to functions which could be
a user-supplied constant, variable or columns.
 Typically, you would use the functions to;
•
•
•
•
•
•
Manipulate numeric and character values.
Convert values of one datatype into values of another datatype.
Modify individual data item.
Format data
Alter data format for display
Summarize query results.
Single Row Functions
 It
is important to note that you can use SQL
functions in the queries either with the columns in
the select list or with the WHERE clause of the
SELECT statement. The format for a function is
follows.
Function
Purpose
Examples
Character
Manipulate
values
character data types
Conversion
Converting values of one data TO_CHAR, TO_DATE,
type to another
TO_NUMBER
of UPPER, LOWER, LENGTH,
SUBSTRING
SELECT function (column or constant),…. FROM
Numeric
Manipulating values of
ABS, TRUNC, ROUND
numeric data types
table_name
Date
Manipulate values of date SYSDATE, ,LAST_DAY
data types operator condition)]
[WHERE function(column
 Single
row functions are divided into the following
types, depending upon the datatype on with they
Character Functions
 UPPER
(column/values). Converts all alphabetic
values into uppercase.
 To
display product numbers along with their names
in uppercase the query is
SQL> SELECT 'Product No '||prodid||' belongs
to '||upper(descrip) FROM
Product;
'PRODUCTNO'||PRODID||'BELONGSTO'||UPPER(DESCRI
P)
-----------------------------------------------------------------------------Product No 100860 belongs to ACE TENNIS RACKET
I
Product No 100861 belongs to ACE TENNIS RACKET
II
Product No 100870 belongs to ACE TENNIS BALLS-
Number Functions
 Number
functions expect numeric input and return
numeric values. Few functions are discussed
bellow.
 ABS(n). Returns the absolute value of a number.
SQL> SELECT abs(100), abs(-100) FROM Dual;
ABS(100) ABS(-100)
--------- --------100
100
 ROUND(n,[m])
returns n rounded to m places right
of the decimal point, if m is omitted, then n is
rounded to 0 places.
Date functions
 Date
functions operate on values of the DATE data
type.
 Oracle stores dates in numeric format internally
representing
•
•
•
•
•
•
•
 The
Century
Year
Month
Day
Hours
Minutes
Seconds.
default format for date is dd-mon-yy.
 The range of dates Oracle offers is between 1 Jan
Continue….
 It
is possible to perform arithmetic operations on
date.
•
•
•
•
date + number
date - number
date - date
date + date
Certain date functions are discussed below.
 ADD_MONTHS(d,n).
•
•
•
Returns the date d plus n months.
The argument n can be any integer.
If d is the last day of the month or if the resulting month has fewer days
than the component of d, then the result is the last day of the resulting
month.
For example to determine 5 months before Jone’s
Continue...
 MONTHS_BETWEEN(d1,
•
•
•
d2):
Returns number of months between the dates.
If d1 is later than d2, the result is positive else negative.
If d1 and d2 are either the same days of the month, or the last days of
months, the result is always an integer, other wise a fractional portion of
the result based on a 31-month is given.
 For
example to calculate the No of months an
employee worked for, the following query is used.
SQL> SELECT ename, round(months_between
(sysdate, hiredate)) FROM Emp;
ENAME
ROUND(MONTHS_BETWEEN(SYSDATE,HIREDATE))
---------- -------------------------------------KING
212
Conversion Functions.
 Conversion
functions convert a value from one
data type to another . Oracle provides the following
3 conversions functions.
•
TO_NUMBER(char):
– Converts char string to number.
•
TO_CHAR(number|date,[fmt]):
– Converts number or date to character format fmt.
•
TO_DATE(char, fmt):
– Converts the character value, representing date, into a date values
according to the fmt specified. If fmt is omitted, it will default to ‘DDMON-YY’.
Continue...
 E.g.
Using TO_NUMBER
SQL>SELECT empno, hiredate FROM Emp
WHERE empno >
to_number(substr('7782clark', 1,4));
EMPNO HIREDATE
---7788
7839
7844
7876
7900
7902
7934
 E.g
--------09-DEC-82
17-NOV-81
08-SEP-81
12-JAN-83
03-DEC-81
03-DEC-81
23-JAN-82
using TO_CHAR
SQL> SELECT to_char(hiredate,'Month DD, YYYY')
FROM Emp;
TO_CHAR(HIREDATE,'MONTHDD,YYYY')
Continue...
 To
display the time the following query is used.
SQL> SELECT to_char(sysdate, 'HH:MI:SS') FROM
Dual;
TO_CHAR(SYSDATE,'HH:MI:SS')
-----------------------------------------------------09:33:11
 Using
 Used
of TO_DATE function.
to convert character string to date format. If
format is not specified the character string is
assumed to contain date in default format.
DECODE function
 This
is one of the most powerful functions.
 It is equivalent to the selection construct
if..then..else..end if or case …end case.
 Syntax
 DECODE (column/expression, search1, result1, [search2,
result2,….]default result)
 The
following query will illustrate the functionality of
DECODE function.
1 SELECT ename, deptno,
2
DECODE(to_char(deptno),
'10','ACCOUNT',
3
'20','RESEARCH',
4
'SOME OTHER
DEPARTMENT')
5* FROM Emp
Nesting functions
 A function
used with in a function is called nested
function.
 Single row functions can be nested to any depth.
 They are evaluated from a innermost to an
outermost function.
SQL> SELECT length (concat(address, city))
FROM Customer;
LENGTH(CONCAT(ADDRESS,CITY))
---------------------------20
24
23
23
22
24
20
Group functions.
 Group
functions process multiple rows of a table
and group them based on a condition. Group
function returns a single row for a group.
The table given below is a list of functions with their
meanings.
Function
Purpose
AVG(DISTINCT|ALL)
To take the average.
COUNT(*|DISTINCT|ALL|expr)
To take the count of rows
satisfying
the condition
MAX(expr)
Returns the maximum value.
Examples using Group
Functions
 To
calculate the average salary of all employees,
the query would be,
SQL> SELECT avg(sal) FROM Emp;
AVG(SAL)
--------2255.7143
 To
calculate the max salary in dept no 30, the
query would be,
SQL> SELECT max(sal) FROM Emp WHERE deptno =
30;
MAX(SAL)
--------2850
Group by clause.
 Used
to create groups of rows in a table.
For example, to find the minimum salary in each
department the following query is issued.
SQL> SELECT deptno, MIN(sal) FROM Emp GROUP BY
deptno;
DEPTNO MIN(SAL)
--------- --------10
1300
20
800
30
950
Nested Groups.
 Used
to form a group with in a group.
 The sequence of columns in the clause should be
from the higher group to the lower group, from left
to right.
E.g. To find out job-wise average salary within each
department, the following query is used
SQL> SELECT deptno, job, AVG(sal) FROM Emp
GROUP BY deptno, job;
DEPTNO
--------10
10
10
JOB
AVG(SAL)
--------- --------CLERK
1300
MANAGER
2450
PRESIDENT
5000
Having Clause
 HAVING
Clause is used to restrict the display of
grouped rows.
 For example, to display the department numbers
and the minimum salary of the employee having
the minimum salary less that 1000, the following
query would do.
SQL> SELECT deptno, min(sal) FROM Emp GROUP BY
deptno
HAVING min(sal) < 1000;
DEPTNO MIN(SAL)
--------- --------20
800
Summary - Functions
 SQL
functions are classified into to , single
row functions and Group functions.
 Single
row functions are divided into 4 types,
character function, numeric function, date
functions and conversion function.
 Oracle
store date in numeric format and is
capable of storing century, year, month, day,
hours, minutes and seconds.
Multiple-table Queries
 Data
is normally distributed over more than one
table. As a result you need to retrieve data from
more than one table.
 Multi-table
queries retrieve data from more than
one table, using a single query statement. This is
achieved by using joins. There are two types of
joins


Equi-join
Non-Equi-join
 Equi-joins
Equi-join Continue...
SQL> SELECT ename, dname FROM Emp, Dept
WHERE Emp.deptno = Dept.deptno;
ENAME
---------KING
BLAKE
CLARK
JONES
MARTIN
ALLEN
TURNER
JAMES
WARD
FORD
SMITH
SCOTT
ADAMS
MILLER
DNAME
-------------ACCOUNTING
SALES
ACCOUNTING
RESEARCH
SALES
SALES
SALES
SALES
SALES
RESEARCH
RESEARCH
RESEARCH
RESEARCH
ACCOUNTING
14 rows selected.
While making joins, columns having the same
name should be prefixed by the table name
Table aliases continue...
SQL> SELECT I.ordid, I.prodid, P.descrip,
I.actualprice
2 FROM
Item I, Product P
3 WHERE I.prodid = P.prodid;
ORDID
PRODID
ACTUALPRICE
--------- ------------ ----------610
100890
58
611
100861
45
612
100860
30
601
200376
2.4
602
100870
2.8
604
100890
58
…..
…..

DESCRIP
-------------------------ACE TENNIS NET
ACE TENNIS RACKET II
ACE TENNIS RACKET I
SB ENERGY BAR-6 PACK
ACE TENNIS BALLS-3 PACK
ACCOUNTING
KING
ACE TENNIS NET
BLAKE
CLARK
Aliases can be up to 30 Characters in Oracle Database.
SALES
RESEARCH
Non-Equi-Join
 When a relationship between two tables is
obtained by using an operator other than equal
(=), it is called a non-equi-join.
SALGRADE
For example, to display employees
having Grade 1
-------salary, the following query would
Namedo.
Type
-------------------GRAD
NUMBER
LOSAL
NUMBER
HISAL
NUMBER
SQL> SELECT E.ename, E.mgr, E.sal, S.grade
FROM
Emp E, Salgrade S
2 WHERE
E.sal BETWEEN S.losal AND
S.hisal AND S.grade = 1;
ENAME
MGR
SAL
GRADE
---------- --------- --------- --------JAMES
7698
950
1
SMITH
7902
800
1
ADAMS
7788
1100
1
Outer Join Continue...
For example, a query that returns employee names
and the respective department names, and also
department names for which no person is
employed.
SQL> SELECT ename, dname FROM
Emp E, Dept D
3 WHERE E.deptno (+) = D.deptno;
ENAME
---------KING
CLARK
MILLER
JONES
SCOTT
ADAMS
SMITH
FORD
BLAKE
MARTIN
ALLEN
TURNER
JAMES
WARD
DNAME
-------------ACCOUNTING
ACCOUNTING
ACCOUNTING
RESEARCH
RESEARCH
RESEARCH
RESEARCH
RESEARCH
SALES
SALES
SALES
SALES
SALES
SALES
Self Join
 Self
join allows to join with same columns of a
EMP
table.
--Name
Type
-------------------------E.g. To retrieve the names ofEMPNO
all employees
and
NUMBER(4)
ENAME
their managers, the query would
be VARCHAR2(10)
JOB
VARCHAR2(9)
MGR
HIREDATE
SAL
COMM
DEPTNO
NUMBER(4)
DATE
NUMBER(7,2)
NUMBER(7,2)
NUMBER(2)
SQL> SELECT E.ename "Employee ", M.ename
"Manager" FROM
Emp E, Emp M
WHERE E.mgr = M.empno;
Employee
---------BLAKE
CLARK
JONES
MARTIN
ALLEN
TURNER
JAMES
WARD
FORD
SMITH
SCOTT
ADAMS
MILLER
Manager
---------KING
KING
KING
BLAKE
BLAKE
BLAKE
BLAKE
BLAKE
JONES
FORD
JONES
SCOTT
CLARK
Summary on Joins.
 Multi-table
queries retrieve data from more
than one table, using a single query
statement.
 Two
type of joins are there. Equi-join and
Non-Equi-Join.
 Equi-Join
uses equality operator (=) to join
two tables.
Set Operators
 Set
operators combine two or more query
results in a single result.
 This
kind of queries consists of two or more
SELECT statements.
 Set
operators are often referred to as vertical
joins.
INTERSECT and MINUS
operators
 INTERSECT
operator is used to retrieve all rows
that are common in the result sets of two or more
queries.
Considering the above example; use INSERSECT
instead of UNION ALL.
SQL>SELECT prodname FROM Sales
WHERE custid = 107
INTERSECT
SELECT prodname FROM Sales
WHERE custid = 108
ORDER by 1
PRODNAME
-----------------------------ACE TENNIS BALLS-6 PACK
 MINUS
operator is used to retrieve all rows
Restrictions on Using Set
Operators
 All
SELECT statements joined by set operators
must have the same type and number of columns
or expressions in the select list.
The following statement is wrong.
SELECT prodname, custid FROM Sales
WHERE custid = 107
UNION
SELECT prodname FROM Sales
WHERE custid = 108
 The
corresponding columns in all SELECT
statements must have the same data type.
The following statement is wrong
SELECT prodname FROM Sales
WHERE custid = 107
UNION
SELECT amount FROM Sales
WHERE custid = 108
Sub Queries / Nested queries
 A subquery
is a SELECT statement that has a
result which is utilized by another SQL statement.
 A subquery is also called a nested query since the
query statement appears inside another statement.
 The SQL statement containing a subquery is called
the parent statement.
A Sample format of a Subquery.
SELECT column1, column2, …..
FROM table
Single-row Subqueries
 Single-row
subqueries return a single value from a
table. The subquery results in then compared to
the value of column(s) in the parent statement.
For example, to find out names of employees who
earn less than the average salary, the following
query is issued. The solution involves two steps,
•
•
Find out the average salary .
Display the employee name who earns less than average salary.
SQL> SELECT ename, sal FROM
Emp
3 WHERE sal < ( SELECT avg(sal)
4
FROM
Emp);
ENAME
SAL
---------- --------MARTIN
1250
ALLEN
1600
Multiple-value Subqueries
 Multiple-value
subqueries return more than one
value to the parent query statement.
 Here the expression in the parent statement is
compared to the list of values returned by the
subquery.
For example, to select employees whose department is in ‘NEW
YORK’ or ‘DALLAS’ the following query is executed.
SELECT ename, deptno FROM
Emp
WHERE deptno IN (SELECT deptno
FROM Dept
WHERE loc IN ('NEW
YORK','DALLAS'))
ENAME
DEPTNO
---------- ---------
Multiple-column subqueries.
 In
Multiple-column subqueries the inner query
returns values for more than one column.
 For example, the following query retrieves the
employee names who earns maximum salary in
each job.
SQL> SELECT ename, sal, job FROM Emp
2 WHERE (sal, job) IN (SELECT max(sal), job
3
FROM emp GROUP BY
job);
ENAME
SAL JOB
---------- --------- --------MILLER
1300 CLERK
ALLEN
1600 SALESMAN
JONES
2975 MANAGER
KING
5000 PRESIDENT
SCOTT
5555 ANALYST
Subqueries with HAVING
Clause
 Subqueries
can also be used in the HAVING
clause
 This query will find out the Jobs having the
average salary less than the average salary of
ANALYST
SQL> SELECT job, avg(SAL)
2 FROM
Emp
3 GROUP BY job
4 HAVING avg(sal) < ( SELECT avg(sal) FROM
Emp
5
WHERE job =
'ANALYST');
JOB
AVG(SAL)
--------- --------CLERK
1037.5
MANAGER
2758.3333
SALESMAN
1400
Correlated Subqueries
 In
correlated subqueries, the inner query is
evaluated repeatedly for each row in the result set
of parent query. I.e the inner query is executed
once for each row considered by the outer query.
 Following steps are executed this type of queries.
•
•
•
•
Get a row from the outer query.
Execute the inner query using the row’s value.
Use the value resulting from the inner query to qualify of disqualify the
row fetched from the outer query.
Continue step 1 to 3 until no row from the outer query remains.
Here is an example that find out employee who earn
a salary less than the average salary of their salary
for their jobs.
SQL> SELECT ename, job, sal
EXISTS Operator
 The
EXISTS operator is normally used with
subqueries to check whether the subquery returns
any rows of query result. If the value exists, it
returns TRUE else FALSE.
 With EXISTS parent does not use the sub query
result. So you can use wildcard * for this.
 For
example, to find out employees who are
managers, I.e. who have at least one employee
reporting to them, the following query would do
1
2
3
SELECT ename, job, deptno
FROM Emp oEmp
WHERE EXISTS (SELECT empno
Summary on Subqueries
 A subquery
is a SELECT statement that has
result which is utilized by another SQL
statement.
 There are four type of subqueries
•
•
•
•
Single-row subquery
Multiple-row subquery
Multiple-value subquery
Correlated subquery
 Single-row
subquery return a single value to
the parent query.