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Chapter:12
Structured Query Language(SQL)
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History
 SEQUEL (Structures English QUery Language) –
early 70’s, IBM Research
 SQL (ANSI 1986), SQL1 or SQL86
 SQL2 or SQL92
 SQL3 or SQL99
 Core specification and optional specialized
packages
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SQL consists of ~20 basic commands
 A lot of research money for each SQL command…
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Standard language for all commercial DBMS
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Why a query language?
Given some data,
how should users
and computer programs
communicate with it?
?
•we need an interface to the data
An Overview of
SQL
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SQL stands for Structured Query Language.
It is the most commonly used relational
database language today.
SQL works with a variety of different fourthgeneration (4GL) programming languages, such
as Visual Basic.
SQL Requirements
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SQL Must be embedded in a programming
language, or used with a 4GL like VB
SQL is a free form language so there is no limit
to the the number of words per line or fixed line
break.
Syntax statements, words or phrases are always
in lower case; keywords are in uppercase.
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STRUCTURE QUERY LANGUAGE(SQL):
The SQL is a language that enables you to
create and operate on relational
databases, which are sets of related
information stored in tables.
=> SQL is a simple query language used
for accessing , handling and managing
data in relational database.
SQL, enables the following:
(i) Creating/modifying a database’s structure
(ii) Changing security settings for system
(iii) Permitting users for working on databases
or tables
(iv) Querying database
(v) Inserting/Modifying/Deleting the database
contents.
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Processing Capabilities of SQL
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Data definition language-The SQL DDL
provides commands for defining relation
schemas, deleting relations, creating indexes,
and modifying relation schemas.
Interactive Data Manipulation Language-The
SQL DML includes a query language based on
both the relational algebra and the tuple
relational calculus.
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Embedded Data Manipulation LanguageThe Embedded form of SQL is designed for
use within general purpose programming
languages such as PL/1,Cobol,Fortan,Pascal
and C.
View Definition-The SQL DDL also includes
commands for defining views.
Authorization-The SQL DDL includes
commands for specifying access rights to
relations and views.
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Integrity-The SQL provides limited forms
of integrity checking. Future products and
standards of SQL are likely to include
enhanced features for integrity checking.
Transaction Control-SQL includes
commands for specifying the beginning
and ending of transactions along with
commands to have a control over a
transaction processing.
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=>Data definition language(DDL): A database
scheme is specified by a set of definition which
are expressed by a special language called a data
definition language (DDL).
 The result of compilation of DDL statements is a
set of tables which are stored in a special file
called Data dictionary (or dictionary).
 i.e. A data dictionary is a file that contains
“Metadata” i.e. , “data about data”
 Classification of sql statement
 All sql statement are instruction to the database
only. And that is where it differs from generalpurpose programming languages like ‘C’ or ‘c++’
or ’BASIC’ etc
DDL perform the following functions:
 It should identify the types of data
division such as data item, record type,
segment, record and database file
 it should give a unique name to each
data –item type, record type, file type,
database etc.
 it should specify the proper data type
 it should specify how the record types
are related to make structures.
 It may define the length of the data
items.
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It may define the range of values that a
data-item can assume.
 checking the error in the data
 Create, alter, and drop schema object
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=>A DATA MANIPULICATION LANGUAGE(DML)
is a language that enables user to access or
manipulate data as organized by the appropriate
data model.
=>By data manipulation, we mean
1.the retrieval of information stored in the
database
2.the insertion of new information into the
database
3.The deletion of information from the database
4.the modification of data stored in the database
=>The DML are basically of two types:
1.Procedure DML required a user to
specify what data is needed and how to
get it.
2. Non-procedure DMLs required a user
to specify what data is needed without
specifying how to get it.
Examples:
INSERT INTO, UPDATE, DELETE,
SELECT, LOCK
=> DCL(Data control Language): It is used to
access to the data base(by GRANTing /
REVOKing etc) and essential to the system
Some MySQL SQL Elements
The MySQL implementation of SQL has
certain elements that play an important role in
defining /querying a database. These basic
elements are:
(i) Literals
(ii) Data types
(iii) Nulls
(iv) Comments
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(i) Literals
 Literals in general, refer to a fixed data value.
The fixed data value may be of character type
or numeric literal.
(ii)Data types
 Data types are means to identify the type of
data and associated operations for handling it.
 Numeric Data Types
 MySQL uses all the standard ANSI SQL
numeric data types. The following list shows
the common numeric data types
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INT
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TINYINT
SMALLINT
MEDIUMINT
BIGINT
FLOAT(M.D)
DOUBLE(M.D)
DECIMAL(M.D)
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Date and Time Types
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The MYSQL date and time data types are:
DATE
DATETIME
TIMESTAMP
TIME
YEAR(M)
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String/Text Types
Most data that you in a database is in
string format. This list describes the
common string data types in MySQL
CHAR(M)
VARCHAR(M)
BLOB or TEXT
TINYBLOB or TINYTEXT
MEDIUMBLOB or MEDIUMTEXT
LONGBLOB or LONGTEXT
ENUM
SQL Data types (from Oracle 9i)
String types
 CHAR(n) – fixed-length character data, n characters
long Maximum length = 2000 bytes.It is inclosed in
single qoutes( ‘ram’)
 VARCHAR2(n) – variable length character data,
maximum 4000 bytes
 LONG – variable-length character data, up to 4GB.
Maximum 1 per table
 Numeric types
 NUMBER(p,q) – general purpose numeric data type
 INTEGER(p) – signed integer, p digits wide
 FLOAT(p) – floating point in scientific notation with
p binary digits precision
21 Date/time type
 DATE – fixed-length date/time in dd-mm-yy form
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SQL Server Data Types
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int, integer: 4 byte integer
smallint: 2 byte integer
tinyint: 1 byte integer
float: 4 or 8 byte floating point number
real: 4 byte floating point number
double precision: 8 bype floating point number
numeric, decimal(precision, scale): exact
numeric, 2 to 17 bytes. Only difference is that
only numeric types with a scale of 0 can be used
of the IDENTITY column.
Destroy a table: drop table table_name
Difference between Char and Vachar datatypes
 The difference between CHAR and VARCHAR
is that of fixed length and variable length.
 The CHAR data types specifies a fixed length
character string and VARCHAR data types
specifies a variable length string.
(iii)Null Values
 If a column in a row has no value, then column is
said to be null , or to contain a null. Nulls can
appear in columns of any data type provided they
are not restricted by NOT NULL or PRIMARY
KEY integrity constraints.
Comments: A comment is a text that is not
executed ; it is only for documentation
purpose. Comments within SQL statements do
not affect the statement execution, but they
may make your application easier for you to
read and maintain. A comment can be given
using double minus sing i.e. - -
SQL COMMAND SYNTAX
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The SQL provides a predefined set of
commands that help us work on relational
databases.
Keywords are words that have a special
meaning in SQL. They are understood to be
instructions.
Commands, or statements, are instructions
given by you to a SQL database.
Arguments complete or modify the meaning
of a clause.
SQL Environment
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Catalog
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Schema
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Commands that define a database, including creating,
altering, and dropping tables and establishing
constraints
Data Manipulation Language (DML)
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The structure that contains descriptions of objects
created by a user (base tables, views, constraints)
Data Definition Language (DDL)
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A set of schemas that constitute the description of a
database
Commands that maintain and query a database
Data Control Language (DCL)
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Commands that control a database, including
administering privileges and committing data
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Queries
SPECIAL OPERATORS
BETWEEN - define range limits
 IS NULL - check if attribute value is
null
 LIKE - check for similar character
strings
 IN - check if attribute value matches a
value within a (sub)set of listed values
 EXISTS - check whether attribute has
a value
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Basic MySQL Operations
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Create database
use database
see data base
Create table
Insert records
Load data
Retrieve records
Update records
Delete records
Modify table
Join table
Drop table
Optimize table
Count, Like, Order by, Group by
More advanced ones (sub-queries, stored procedures,
triggers, views …)
Syntax to Create database
Create database databasename ;
 Create a database (make a directory) whose name is
MyDB
 mysql> create database MyDB;
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Select database to use
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mysql> use MyDB;
Database changed
What tables are currently stored in the MyDB
database?
mysql> show tables;
Empty set (0.00 sec)
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What are the current databases at the server?
mysql> show databases;
+--------------+
| Database |
+--------------+
| mysql
|
| test
|
+--------------+
mysql is a database (stores users’ password) used
by system.
=>CREATE TABLE COMMAND

CREATE TABLE – defines a table and its
columns, data types and sizes are supplied
for each column.
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CREATE TABLE Table_Name (column_specifications)
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Syntax;
<table-name>
(column name data tpes[size], column name
data tpes[size],….);
Example: CREATE TABLE employee ( ecode int,
ename char(20),sex char(1), grade char(2),
gross decimal);

CREATE TABLE
Constraint; A CONSTRAINT IS A
CONDITIONAL OR CHECK APPLICABLE
ON A FIELD OR SET OF FIELD.
There are two type of constraints
Column constraint: It apply only to individual
columns
Table Constraint: It apply to groups of one or
more columns.
Syntax:
CREATE TABLE table-name ( column-name
data type[size] column constraint, columnname data type[size] column constraint, ….);
employee
( ecode int NOT NULL,
ename char(20) NOT NULL,
sex char(1) NOT NULL,
grade char(2),
gross decimal);
 Different Constraints:
 Unique Constraints
 Primary key Constraints
 Default Constraints
 Check Constraints
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CREATE TABLE
Unique Constraints: This Constraints
ensures that no two rows have the same
value in the specified columns.
 CREATE TABLE employee
( ecode int NOT NULL UNIQUE,
ename char(20), NOT NULL
sex char(1), NOT NULL
grade char(2),
gross decimal);

Primary key Constraint: It is a set of column
or columns that uniquely identify a row in a
relation.
 CREATE TABLE employee
( ecode int NOT NULL PRIMARY KEY,
ename char(20), NOT NULL
sex char(1), NOT NULL
grade char(2),
gross decimal);
Default Constraint: A default value can be
specified for a column using the default clause.
When a user does not enter a value for the
column(having default), automatically the
defines default value is inserted in the field.
 CREATE TABLE employee
( ecode int NOT NULL PRIMARY KEY,
ename char(20), NOT NULL
sex char(1), NOT NULL
grade char(2) DEFAULT=‘E’,
gross decimal);
Check Constraints: This constraint limit values
that can be inserted into a column of a table.
 CREATE TABLE employee
( ecode int NOT NULL PRIMARY KEY,
ename char(20), NOT NULL
sex char(1), NOT NULL
grade char(2) DEFAULT=‘E’,
gross decimal CHECK(GROSS>2000));
=>When a check constraint involves more
than one column from the same table, it is
specified after all the columns have been
defined.
employee
( icode char(5) NOT NULL PRIMARY KEY,
descp char(20), NOT NULL
ROL integer,
QOH integer,
CHECK (ROL<QOH)
);
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CREATE TABLE
Applying Table Constraints: The Table
constraints appear in the end of the table
definition.
CREATE TABLE items
( icode char(5) NOT NULL,
Descp char(20) NOT NULL,
ROL integer,
QOH integer,
CHECK (ROL<QOH),
UNIQUE (icode,descp));
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mysql> show tables;
+--------------------+
| Tables_in_MyDB |
+--------------------+
| student
|
+--------------------+
1 row in set (0.00 sec)
mysql> describe student;
+---------------+----------------------+------+------+----------+--------+
| Field
| Type
| Null | Key | Default | Extra |
+---------------+----------------------+-------+-----+-----------+-------+
| student_ID | int(10) unsigned |
|
|0
|
|
| name
| varchar(20)
|
|
|
|
|
| major
| varchar(50)
| YES |
| NULL |
|
| grade
| varchar(5)
| YES |
| NULL |
|
+---------------+----------------------+-------+------+----------+-------+
4 rows in set (0.00 sec)
The SELECT Command
 The SELECT command of SQL lets you make
queries on the database. A query is a command
that is given to produce certain specified
information from the database table(s).
 SELECT statement is used as given below;
 SELECT <column name>, <column name> ,
…FROM <table name> ;
 Example: SELECT Empno,Empname FROM emp;
SELECT Statement
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Used for queries on single or multiple tables
Clauses of the SELECT statement:
 SELECT
 List the columns (and expressions) that should be returned
from the query
 FROM
 Indicate the table(s) or view(s) from which data will be obtained
 WHERE
 Indicate the conditions under which a row will be included in
the result
 GROUP BY
 Indicate columns to group the results
 HAVING
 Indicate the conditions under which a group will be included
 ORDER BY
 Sorts the result according to specified columns
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List the selected column of a table
 SELECT empno,job,sal FROM emp;
 List the all column of a table
 * is wildcard character - gives “all rows”
 SELECT * FROM emp;
 Reordering columns in query Results
 SELECT job,empno,sal FROM emp;
 Eliminating Redundant data (with keyword
DISTINCT): The DISTINCT keyword
eliminates duplicates rows from the results of a
SELECT statement.
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Example: SELECT DISTINCT city
FROM suppliers;
 Selecting From All the Rows-ALL
Keyword: The result retains the
duplicates output rows. It is just the
same as when you specify neither
DISTINCT nor ALL.
 EXAMPLE:
 SELECT ALL city FROM suppliers;
Selecting Specific Rows-Where clause: The
tables can contain unlimited rows. If you want
to view selected rows from the table.the
WHERE clause in SELECT statement
specifies the criteria for selection of rows to be
returned.
Syntax:
SELECT column name, column name,....
FROM table name WHERE condition;
 EXAMPLE:
 SELECT empname,sal FROM emp WHERE
sal>2900;
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List all the members not from ‘DELHI’

SELECT * FROM suppliers WHERE city <
> ‘ DELHI’ ;
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Logical Operator: The logical operators OR
,AND and NOT are used to connect search
conditions is the WHERE clause.
1.
To list the employees details having
grade ‘E2’ or ‘E3’ from the table
employee
SELECT ecode,ename,grade,gross FROM
employee WHERE(grade=‘E2’ OR
grade=‘E’);

2. To list the employees details having
grades ‘E4’ but with the gross<9000
from the table employee
SELECT ecode,ename,grade,gross FROM
employee WHERE(grade=‘E4’ AND
gross<9000);
3. To list all the employees details whose
grade are other than ‘G1’.
SELECT ecode,ename,grade,gross FROM
employee WHERE(NOT grade=‘G1’);
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CONDITION BASED ON A RANGE: The
BETWEEN operator defines a range of values
that the column values must fall into make the
condition true.yhe range includes both lower
values and the upper value.
To list the item whose QOH falls between 30
to 50(both inclusive).
SELECT icode ,descp,QOH FROM items
WHERE QOH BETWEEN 30 and 50.
SELECT icode ,descp,QOH FROM items
WHERE QOH NOT BETWEEN 30 and 50.
CONDITION BASED ON A LIST: The IN
operator selects values that match any value
in a given list of values.
 To display a list of members from ‘DELHI’,
‘MUMBAI’, ‘CHENNAI’, OR ‘ BANGALORE’
CITIES.
 SELECT * FROM members WHERE city IN
(‘DELHI’, ‘MUMBAI’, ‘CHENNAI’,
‘ BANGALORE’ );
=> SELECT * FROM members WHERE city
NOT IN (‘DELHI’, ‘MUMBAI’, ‘CHENNAI’,
‘ BANGALORE’ );
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CONDITIN BASED ON PATTERN
MATCHES: The string matching operatr,
LIKE, for comparisons on character strings
using patterns. Patters are described
using two special wildcard characters.
 percent(%): The % character matches
any substring.
 underscore( _ ): The _ character
matches any one character.
 Patterns are case sensitive i.e. , upper
case characters dot not match lower case
characters or vice –versa.
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The keyword NOT LIKE is used to select
rows that do not match the specified pattern of
characters.
In order for patterns to include the special
pattern characters(that is, %,_), SQL allows
the specific of an escape character.
The escape character is used immediately
before a special pattern character to indicate
that the special pattern character is to be
treated as a normal character.
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“San%” matches any string beinning with “San”.
“%idge%” matches any string containing “idge” as a
substring, for example “ridge” , Bridge”, etc.
“ _ _ _ _” matches any string of exactly 4
characters.
“ _ _ _ _ %” matches any string of at least 4
characters.
1. To list members which are in areas with pin
codes starting with 13.
SELECT firstname, lastname,city FROM members
WHERE pin LIKE “13%”;
2.To list employees who have four letter
first names ending with “ D”.
 SELECT empno, empname FROM emp
WHERE empname LIKE “ _ _ _ D”;
 3.To list members which are not in areas
with pin codes starting with 13.
 SELECT firstname, lastname,city FROM
members WHERE pin NOT LIKE “13%”;
 SEARCHING FOR NULL: The NULL
value in a column can be searched for in a
table using IS NULL in the WHERE
clause.
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SELECT empno, empname, job FROM emp
WHERE DeptNo IS NULL;
SEARCHING RESULTS- ORDER BY CLAUSE:
The ORDER BY clause allows sorting of query
results by one or more columns. The sorting can be
done either on ascending or descending order. the
data in the table is not sorted; only the results that
appear on the screen are sorted,
Syntax: SELECT column name,… FROM table
name WHEE condition ORDER BY column name.
SELECT * FROM employee ORDER BY ename;
SELECT empno , empname , job FROM emp
WHERE sal> 2500 ORDER BY ename ;
SELECT * FROM employee ORDER BY ecode
DESC;
DESC: descending order
 ASC: Ascending order
 SELECT * FROM employee ORDER By
grade DESC , ename ASC;
 SIMPLE CALCULATION:
 DUAL table is a small worktable , which
has just one row and one column.
 SELECT 4*3 FROM dual;
 SELECT sysdate FROM dual;
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 What is an aggregate function?
An aggregate function summarizes the results of an
expression over a number of rows, returning a single
value. The general syntax for most of the aggregate
functions is as follows: aggregate_function
([DISTINCT|ALL] expression)
 Commonly used Aggregate functions
 Some of the commonly used aggregate functions
 are :
• SUM
• COUNT
• AVG
• MIN
• MAX
1.Avg Function
The AVG() function returns the average value of a numeric column.
Query 1: If we want to calculate the AVG of all the salaries
in
the organization the SQL would be
SELECT AVG(SALARY) FROM EMPLOYEE
62,500
Is this what we expect????
Employee table has 7 records and the salaries are
50,000+60,000+50,000+70,000+75,000+70,000+null/7 =
53571
But we obtained 62500 from the query? Why is this so????
AVG (Continued….)
Remember : COUNT(*) is the only function which won’t
ignore Nulls. Other functions like SUM,AVG,MIN,MAX they
ignore
Nulls. What it means is in the previous query the salary value
for a particular employee was NULL. So the query
SELECT AVG(SALARY) FROM EMPLOYEE
would ignore nulls and the way the average is calculated then
would
be
50,000+60,000+50,000+70,000+75,000+70,000/6 = 62500
AVG (Continued….)
From the information given in the previous slide what do you think
would be the output of the following query
Select COUNT(*),COUNT(SALARY) FROM EMPLOYEE;
It would be
COUNT(*) COUNT(SALARY)
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6
Because COUNT(*) is not going to ignore the Nulls in the result
whereas COUNT(SALARY) is going to ignore the Nulls.
2.COUNT
The SQL COUNT aggregate function is used to count the
number of rows in a database table.
 The SQL COUNT syntax is simple and looks like this:
COUNT({*[DISTINCT | ALL] expr})
FROM Table1
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If we want to count the number of records in table empl,
we will use the following SQL COUNT statement:

SELECT COUNT(*) “Total”
FROM empl;
 The result of this SQL COUNT query will be:
Total
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3.MAX
 The SQL MAX aggregate function allows us to select
the highest (maximum) value for a certain column.
 The SQL MAX function syntax is very simple and it
looks like this:
MAX([DISTINCT | ALL] expr)
 If we want to display maximum salary from table
empl SQL MAX expression:
SELECT MAX(sal) “Maximum Salary”
FROM empl;
Maximum Salary
5000.00
4.MIN
 The SQL MIN aggregate function allows us to select
the lowest (minimum) value for a certain column.
 The SQL MIN function syntax is very simple and it
looks like this:
MIN([DISTINCT | ALL] expr)
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If we want to display the joining date of senior most
employee the following SQL MIN expression is used :
SELECT MIN(hiredate) “Minimum Hire Date”
FROM empl;
Minimum Hire Date
1990-12-18
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5.sum
sum is an aggregate function. It returns the sum of its
numeric-expressions for each group indicated in the group by
clause.
Query 1: To find the sum of all salaries in the organization:
SELECT SUM(SALARY) FROM EMPLOYEE;
375000
Query 2: To find the sum of the salaries grouped by dept
SELECT SUM(SALARY) FROM EMPLOYEE GROUP BY
DEPT_NAME
Types of sql functions
(i)Single-Row Functions
 Single-row functions return a single result row for every
row of a queried table or view.
 Examples of single row functions are the functions are
text/Character functions such as year(),day(),etc.
(ii) Multiple Row or Group Functions work with data of
multiple rows at a time and return aggregate value.
Examples of multiple row functions are the group functions
i.e. , sum(),count(),max(),min(), Avg()etc.
A single row function works with the data of single row
at a time and returns a single result for each row queried
upon ; a multiple row function works with the data of
group of rows at a time and returns a single result for that
Grouping result – group by
 The GROUP BY clause combines all those records
that have high identical values in a particular field
or a group of fields. This grouping results into one
summary record per group if group-functions are
used with it.In other words ,the GROUP BY clause is
used in SELECT statements to divide the table into
groups. Grouping can be done by a column name,or
with aggregate functions in which case the
aggregate produces a value for each group.
 Ex: SELECT job ,COUNT(*),sum(comm)
FROM emp GROUP BY job ;
GROUP BY applies the aggregate functions
independently to a series of groups that are defined
by having a field value in common.
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NESTED Groups - Grouping on multiple
Columns
With GROUP BY clause ,you can create groups
within groups. Such type of grouping is called
Nested grouping. This can be done by specifying in
GROUP BY expression, where the first field
determines the highest group level, the second field
determines the second group level, and so on. The
last field determines the lowest level of grouping.
See there are multiple records having same value
for depno,we can group records on the basis of
field Deptno.
For instance ,if you want to count the number of
employees in each group ,you need to issue a query
statement as given below:
SELECT COUNT(empno) FROM empl
GROUP BY Deptno;
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Result produced by the query is
Count(empno)
3
5
6
But can you make out ,these are employee-counts
for which departments? To get this information , you
may modify the SELECT list as:
 SELECT Deptno, COUNT(empno)
FROM empl
GROUP BY Deptno ;
Deptno count(empno)
10
3
20
5
30
6
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One thing should be kept in mind is that while grouping
, you should include only those values in the selected
list that either have the same value for group or contain
a group(aggregate) function i.e. , a group expression. Like
in the above query, the first expression Deptno field has
one (same) value for a group and the other expression
COUNT(empno) contains a group function.
A non group field (or expression) is the field that has
different values in the rows belonging to group.
In the select list of a group ,only those fields or
expressions state be included that either return single
value for a group are constants.Otherwise you may not
get authentic results.
Placing condition on groups-HAVING
Clause:
The HAVING clause places conditions on
groups in contrast to WHERE clause that
places conditions on individual
while
WHERE conditions cannot include aggregate
functions, Having conditions can do so.
SELECT avg (gross), sum(gross)
FROM employee
GORUP BY grade
HAVING grade=‘E4’;

To display the jobs where the number of
employee are less than 3.
 SELECT job count(*) FROM emp
GROUP By job Having count(*)<3;
 SCALAR EXPRESSIONS WITH
SELECTED FIELD: SQL allow to place
scalar expressions and constants among
the selected fields.
 SELECT salesman_name , comm * 100
FROM salesman;






PUTTING TEXT IN THE QUERY OUTPUT: To
insert comment or symbol with every row of the
output.
SELECT salesman_name , comm * 100 , ‘%’
FROM salesman;
SELECT salesman_name , ‘gets the
commission’, comm * 100, ‘%’ FROM salesman;
CREATING TABLE FROM EXISTING TABLE:
To create the table without going through the
usual data definition process. this can be done
by SELECT statement with CREATE TABLE.
CREATE TABLE orditem AS ( SELECT icode,
descp FROM items WHERE QOH<ROL );
A new table create from an existing table with
help of SELECT INTO.
 SELECT icode, descp INTO orditems
FROM items WHERE QOH<ROL ;

Basic Insert: Inserting a Tuple into a Table




Insert one tuple into table:
insert into table_name[(column_list)]
values(value_list)
Ex: specify values for all attributes:
insert into STUDENT values(‘Mike’, 1, 3.8, 3, ‘CS’)
Ex: specify values for only some attributes:
insert into STUDENT(name, regno, level)
values (‘Jenny’, 2, 1)
NOTE: in SQL, strings are surrounded by single
quote, not double quote. Double quotes surround
identifiers that contain special characters. To
include a single quote in the string use two single
quotes (eg.,’it’’s good’)
INSERTING THE RESULTS OF A QUERY:
inserting COMMAND CAN ALSO be used to
take or drive values from one table and place
them in another by using it with a query.
 INSERT INTO branch1
SELECT * FROM branch2 WHERE
gross>7000.00;
=> THE DELETE COMMAND: To removes rows
from a table.
SYNTAX: DELETE FROM <tablename>
[ WHERE<SONDITION> ];
SQL> DELETE FROM employee WHERE
gross<2200.00;

Mysql> DELETE FROM student;
Will delete ALL student records
=> The UPDATE COMMAND: The UPDATE command
specifies the rows to be changed using the
WHERE clause, and the new data using the SET
keyword.
=> SYNTAX: UPDATE table name SET which
columns to change
WHERE condition
 Example
mysql> UPDATE student SET grade='B' WHERE
name='Shannon';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
Mysql> UPDATE items SET ROL=250;
Mysql> UPDATE items SET ROL=400 WHERE
ROL=300;
=>UPDATING MULTIPLE COLUMNS:
Mysql> UPDATE items SET ROL=400,QOH=700
WHERE icode<‘I040’;
 Using Expressions in UPDATE: Scalar
expressions can also be used in the SET
clause of the UPDATE command.
Mysql> UPDATE employee SET
gross=gross+900;
 UPDATING TO NULL VALUES: The NULL
values can also be inserted just as other
values.
Mysql> UPDATE employee SET grade=NULL
WHERE grade=‘E4’;
The CREATE VIEW COMMAND: A view
is a virtual table with no data , but can be
operated like any other table;
 CTREATE VIEW taxpayee AS SELECT *
FROM employee WHERE gross> 8000;
 Note : The SELECT statement used in
a view definition cannot include:
 ORDER BY clause
 INTO clause
 CREATE VIEW taxpaee ( empcode,
empname,sex,empgrade,empgross) AS
SELECT * FROM employee WHERE
gross>8000;

SOME BUILD – IN FUNCTIONS:
 1.LOWER(character expression ): This
function converts a giving character
expression into lowercase.
 Syntax : LOWER(char);
 Description: returns the argument char
, with all latter lowercase;
 SQL> SELECT LOWER(‘MR.ANIL’)
lowername1, LOWER(‘MR. Maithili’)
“Lowername2” from dual;






2.UPPER(character expression ): This
function converts a giving character
expression into uppercase.
Syntax : UPPER (char);
Description: returns the argument char ,
with all latter lowercase;
SQL> SELECT UPPER (‘MR.ANIL’)
lowername1, UPPER(‘MR. Maithili’)
“Lowername2” from dual;
Output:
3. Replicate(char-expn,no-of-time): To repeats yhe
given char-expn the no-of –times .the no-of-times
has to an integer.
mysql>SELECT replicate(“*#”,4) FROM Dual;
Output: *#*#*#*#
4.SUBSTR: This function extract a substring
from a given string.
 Syntax: SUBSTR(char, m[, n])
 Description: Returns a portion of char,
beginning at character m, n character long. if
m is 0.it is treated as 1.if m is positive ,
negative. If n is less than 1,a null is returned.
SQL> select SUBSTR(‘Pointer’, 3,2) “subs”
from dual;
Output: in
5.getdate( ): it return the current system date.
Mysql>SELECT getdate( ) FROM Dual;
6.CONCAT:
 Syntax: CONCAT(char1,char2).
 SQL>select CONCAT(ename, ecode)
“name and code” from emp where
empno =7900 or empno=7788.
7. INITCAP:
Syntax: INITCAP(char)
 Description: Returns the given
arguments char, with the first letter of
each word in uppercase, all other
letters in lowercase.
 SQL>select INITCAP( ‘the soap’)
“Capitals” from dual;
8.LPAD: This function left-pads (i.e., inserts the left side)
the giving character to given string to reach at given
width.
 Syntax:LPAD(char1, n [, char2])
 Description: Returns argument char1,left-padded to
length n with the sequence of characters in argument
char2.
 The arguments n is the total length of the return
values as it is displayed on the screen.
 SQL> select LPAD(‘hello’,15,’*.’) “left padded
ename” from EMP where empno=7788;
9.RPAD: function RPAD is similar to that of
LPAD. only difference is that the specified
character are right padded.
=>Join is a query that combines rows from
two or more tables. that is Join is used to
give the data from multiple table with single
query. The function of combining data from
multiple table is called Joining.
SQL> SELECT patient_no, description,
normal_charge,charge FROM billed,item
WHERE billed.item_code= item.item_code;
CARTESIAN PRODUCT: In unrestricted join
or Cartesian product of two table ,all
possible concatenations are formed of all
rows of both the tables.
 SELECT * FROM EMP,DEPT ;
=>A Table Alias is a temporary label
given along with table name in FROM
clause.
SQL>SELECT DISTINCT patient_no,
phy_id FROM treats WHERE phy_id
IN(8887,8886,8883,8882);
Types of Join
1. Inner or Equi-Join
2.Self Join
3.Outer Join
(a). Left outer Join
(b). Right outer Join
(c). Full outer Join
4.Natural Join
1. Inner or Equi-Join: The join in which
columns are compared for equality, is
called Equi-Join. OR INNER Join.
Inner Join is used to give the matching
records from Joined tables.
For example: Table A.equi join table B
SQL>SELCT billed.patient_no,
date_discharged, charge
FROM billed,patient WHERE
patient.patient_no =billed.patient_no;
=>Non-Equi Joins: A non- equi-join is a
query that specifies some relationship
other than equality between the columns.
2.Natural Join: The Join in which only one
of the identical columns(coming from
joined tables) exits, is called Natural Join.
3. Self Join: A table Joined with itself is
called self join
SQL> select.*,sup2.supp# from suppliers
where sup1.supp#<>sup2.supp# and
sup1.city= sup2.city;
Outer Join: Outer Join selects all the rows
that satisfy the join condition and those
rows from one table for which no rows
from the other table satisfy the join
condition.
Left-Outer Join: Left outer jon give the
results as combination of matching record
from both the table plus remaining record
from left side tables.
It is denoted by +
For left join + is used to the right side table
variable
SQL>select sname, email, feebal from
student s, fees f where s.sid =f.sid (+);
Right-outer Join: It Gives the results as
combination of matching records plus
remaining record from right sides tables.
SQL>select sname,email,feebal from
student s,fees f where s.sid(+)=f.sid;
Full outer-join: It Gives the results as
combination of matching records and
remaining record from left sides table
plus remaining record from right sides
tables.
SQL>select sname, email, feebal from student s,
fees f where s.sid(+)=f.sid(+);
=>UNION: The SQL UNION operator allows
manipulation of results returns by two or
more queries by combining the results of
wach query into a single result set.
Mysql> SELECT * FROM A UNION
SELECT * FROM B;
 It remove the duplicate rows from results.
 if the all option is used,all rows, including
duplicate are included in the results.
 SELECT statement UNION [ALL]
SELECT statement;
RULE OF using UNION OPERATOR:
1. Both the SELECT statements must be
UNION compatible, that is, the select-list of
SELECT statement must have same number of
column having similar data type and order.
Mysql> SELECT ecode,ename FROM branch1
UNION
SELECT ecode,ename FROM branch2;
2. The ORDER BY clause occurs only at the end
of the UNION statement. It can’t be used
within the individual queries that make the
UNION statement.
3. The GROUP BY and HAVING clause are
allowed only within individual queries . These
clause cannot be used to affect the final result
set.
ALTERING TABLE: It is used to change
definitions of existing tables.
1.To add a column
2. To add an integrity constraint
3. To redefine a column (data type, size , default
value).
ADDING COLUMNS:
SYNTAX:
ALTER TABLE <table name> ADD <column
name> <data type> <size> [<constraint name>];
SQL>ALTER TABLE Emp ADD (tel_number
integer);
=>The new column will be added with NULL
values for all rows currently in the table.
Mysql> ALTER TABLE Emp ADD
(tel_number integers);
Modifying Column Definitions:
SYNTAX:
ALTER TABLE <table name> MODIFY
(column name new data types (new
size));
SQL> ALTER TABLE Emp MODIFY (Job
char(30));
Removing Integrity Constraints
To drops the primary key of table DEPT
SQL> ALTER TABLE dept DROP PRIMARY
KEY CASCADE ;
ENABLING OR DISABLING CONSTRAINTS: The
ALTER TABLE command can be used for
enabling or disabling a constraint.
SQL> ALTER TABLE products ENABLE
pk_produce_01 ;
SQL> ALTER TABLE products DISABLE UNIQUE
(serial#) ;
TRUNCTING TABLE: It allows users to delete
information from a table quickly, using
TRUNCTING COMMAND.
SQL> TRUNCTING TABL products;
=>TRUNCATE is a part of DDL unlike DELETE
which is a part of DML
THE DROP TABLE COMMAND: To drop a
table from databse.It must be an empty
table
SQL> DELETE FROM items ;
SQL> DROP TABLE items;
SQL> TRUCATING TABLE items;
 A table with rows in it cannot be dropped.

THE DROP VIEW COMMAND:
To delete a view from the
database ,the DROP VIEW
command is used.
Mysql>DROP VIEW taxpayee;
To drops the view taxpayee
from database. When a view is
dropped, it does not cause any
change in its base table after
the removal of view taxpayee.