Database Systems - Introduction to SQL (Chapter 3/1)

S Q L
•What is SQL?
•Importance of SQL
•Should you learn SQL?
•Pre-requisites
•SQL Topics Covered

What is SQL?
This slide and next two slides will give you information on SQL for you to
decide if you want to take this course to learn SQL.
SQL is an abbreviation for “Structured Query Language”. It is a language used
to query data present in relational databases.
Though it is called a query language, the language can be used to add data to
a database, modify existing data in the database and delete data from the
database.
SQL is similar to other programming languages such as C, C++ and Java, but
with one major difference: it is primarily non-procedural unlike other
general programming languages which are procedural. Its queries tell an
RDBMS what to retrieve and not how to retrieve.

Importance of SQL
SQL is the primary database language used in thousands of applications.
SQL is the main, or almost the only language, used in all most all
relational database management systems.
All market leading database management systems such as Oracle, MS SQL
Server and DB2 support SQL.
Most popular free database management systems such as MySQL, SQLite
and postgreSQL also support SQL.
Most of the modern database applications for domains such as banking
and telecom are written using SQL.
SQL can be used from various other languages such as C, C++, C#, Java,
PHP, Python, etc., for writing database applications.

Should You Learn SQL?
You should definitely learn SQL if you want to become a database
professional.
If you are a student and studying a database related course, you
may want to take this course to improve your knowledge about
SQL and it may help you understand the database course better.
Even if you already know SQL, you may want to take this course to
refresh your knowledge of SQL.
If you are a technical project manager, have some idea of what is
SQL and would like to know a bit more about SQL in shortest
possible time, you may want to take the course.

Pre-requisites
It is preferable if you to meet the following pre-requisites to benefit
from this course on SQL:
1. You should already be familiar with database concepts, particularly
relational database systems (relational databases and relational
database management systems)
2. You should have knowledge of at least one programming language
such as C, C++, C#, Java, PHP, python, etc., to appreciate SQL.
3. You should have a computer system such as Windows PC.
4. You should be able to download and install at least MySQL database
software for practicing SQL. Alternatively, you can use any other
relational database management system such as Oracle, SQL Server,
and SQLite

SQL Topics Covered
The course on SQL covers the following topics:
 Introduction to SQL
 Database Structure
 MySQL Setup
 SQL Basics
 SQL - DDL
 SQL - DML
 SQL - DCL

1. Introduction to SQL
 What is SQL?
 SQL – A Query Language
 SQL Vs Other Languages
 History of SQL
 Importance of SQL

What is SQL?
SQL is an abbreviation for “Structured Query Language”.
SQL is a language used to build database applications that need
to query relational databases.
SQL has statements such as CREATE, SELECT, INSERT, UPDATE,
DELETE, etc., just like there are statements such as assignment
statement, if statement, while statement, etc., in general
purpose programming languages such as C, C++ and Java.
SQL is a language for databases just like C, C++ and Java are
languages for general purpose programming.

SQL - A Query Language
SQL is a Query Language.
Query means retrieval of required data from databases. In a general sense it
may also mean any statement of SQL that can be used to query database,
modify the database or do any other operation on the database.
For example, if a database contains data about all employees of a company,
the following could be some sample queries expressed in plain English
language:
• Retrieve salary of employee ‘Rahul’.
• Retrieve all data about employees of department ‘Research’.
• Retrieve names of employees whose salary is more than Rs 1,00,000.
Above queries can be represented in SQL to retrieve data from the database.

Categories of SQL Statements
As already mentioned, SQL not only contains query statements,
it also contains various other statements required for database
management and applications.
The broad categories of SQL Statements are as follows:
Data Definition Language (DDL) Statements
Data Manipulation Language (DML) Statements
Data Control Language (DCL) Statements.
Note that SQL standard document does not use the terminology
DDL, DML and DCL but most of the database text books use it.

SQL - DDL Statements
SQL – DDL statements are used to create relational data
structure in the database.
The DDL statements are used to create database objects such as
tables and views, alter them and drop them.
Sample DDL statements are:
• CREATE TABLE - Used to create a table.
• ALTER TABLE – Used to alter definition of a table.
• DROP TABLE – Used to remove a table from database.

SQL – DML Statements
SQL DML statements are used to query as well as modify the
database.
Sample DML statements are as follows:
• SELECT - Used to retrieve data from one or more tables.
• INSERT - Used to add data to a table.
• UPDATE – Used to modify data in a table.
• DELETE - Used to delete data from a table.

SQL – DCL Statements
SQL DCL Statements are used to control access to the database,
control transactions and control user sessions with the
database.
Sample DCL statements are
• CONNECT - Used to establish connection to a database.
• SET TRANSACTION – Used to set various properties of
transactions.
• GRANT – Used to provide privileges to access database
objects.
• COMMIT - Used to make a transaction changes permanent in
the database.

History of SQL
• 1974 – D. Chamberlin of IBM defined SEQUEL
• 1975 – SQUARE language was defined
• 1976 – Revised SEQUEL/2 was renamed to SQL

.
• 1987 - First ISO Standard for SQL was published.
• 1989 - ISO published an addendum on IEF
• 1992 - First major revision, aka, SQL2 or SQL-92.
• Other revisions were released in 1999 (O-R features),
2003 , 2008 and 2011
History of SQL (contd…1)

Importance of SQL
 SQL is the most widely used language for Relational Database
Management Systems.
 SQL is the primary database language used in thousands of
database applications.
 Standard exists for SQL; standards ensure database applications
are portable across various database management systems.
 Supported by products of many organizations.
 SQL influences even other standards.

Importance of SQL (contd…1)
 All market leading database management systems such as
Oracle, MS SQL Server and DB2 support SQL.
 Most popular free database management systems such as
MySQL, SQLite and postgreSQL also support SQL.
 Most of the modern database applications for domains
such as banking and telecom are written using SQL.
 SQL can be used from various other languages such as C,
C++, C#, Java, PHP, Python, etc., for writing database
applications.

What You Have Learnt !
 SQL is a language for databases.
 SQL has statements like statements in programming
languages such as C, C++ and Java.
 SQL has DDL, DML and DCL statements.
 SQL Originated from work started at IBM in 1974 by
D. Chamberlin.
 SQL is SEQUEL/2 renamed in 1976.
 First ISO Standard for SQL was published in 1987.
 First major standard is SQL 2 or SQL 1992.
 SQL is the most widely used database query
language in the world.

2.Relational Database Structure
 Organization of Database Objects
 Database Objects Directly in the Database
 Database Objects in Schemas
 Database Objects in Catalogs
 Schema
 Catalog

Organization of Database Objects
A database object is an element such as a table in a database.
Some of the Database organizations are as follows:
One or more database objects such as tables directly in the
database.
One or more schemas where each schema contains database
objects such as tables.
One or more catalogs where each catalog contains one or
more schemas.
It is possible that some database could have a different
organization for its objects.

Database Objects Directly
in the Database
Table 1
Table 2
View 1
Database directly containing tables, views, etc.
Index 1
Database

Database Objects in
Schemas
Database containing tables, views , etc., in schemas of
a database.
Database
Index 1 View 1Table 2
Table 1
Schema 1
Schema 3
Schema 2

Database Objects in
Schemas of Catalogs
Database
Index 1
View 1Table 2
Table 1
Schema 1
Schema 3
Schema 2
Catalog 1
Catalog 2

Object Containment Hierarchy
Database
Catalog
Schema
Table View Index
Catalog Catalog
Schema Schema

Schema
A schema is a named collection of database objects such
as tables and views.
Each schema has a name.
SQL standard provides statements to create and destroy
schemas.
Most RDBMSs support the concept of schemas.
Some RDBMSs simulate schema using user name or owner
name.

Catalog
A catalog is a named collection of schemas.
Each catalog has a name.
SQL standard does not specify how to create a catalog.
The creation and destruction are specific to an RDBMS.
Catalog == Database if an RDBMS does not support
catalogs explicitly.
An RDBMS installation usually supports one or more
databases.

1. SQL operates on the objects of relational database structure.
2. An installation of an RDBMS usually supports one or more databases.
3. Method of creation and destruction of databases is not part of SQL
standard and hence the method varies for each RDBMS.
4. The physical database structure used to implement the relational
database structure could be different for each RDBMS.
5. A database consists of database objects directly in the database or
the objects could be in one or more schemas which could be in one
or more catalogs.
6. Some RDBMSs use user ID for simulating schemas.

3. MySQL Setup
 Downloading and Installing MySQL
 Starting MySQL Database Service
 Using MySQL Command Line Tool
 Creating Database
 Creating User Accounts

MySQL Download
• We will use SQL command line tool of MySQL RDBMS for
demonstrations.
• If you do not have MySQL on your machine, you can
download MySQL Community Server from
(http://www.mysql.com/downloads/mysql/)
• Install it on your Windows PC.
• Make sure the MySQL server is running before you start
its client tool as shown in the next slide.

MySQL
Command Line Client
You can access the tool from Programs menu as shown below:

MySQL
Starting Command Line Client From Windows
Command Shell
• You can also directly execute the tool from Windows
Command Shell.
• The tool program file is mysql.exe
• It will be present in the following directory:
C:Program FilesMySQLMySQL Server 5.1bin
• You can invoke it as follows:

MySQL
User and Database Creation
Use CREATE DATABASE statement of MySQL to create a database, say,
mdb, a database for a mobile software development company.
Using super user ID root is not a good idea for training purpose to avoid
doing any unintended costly changes to the databases. Hence,
create a sample user “mdba” with password “mdba123” as shown
in the following screenshot and make the user a database
administrator for the database by granting all permissions on the
database to the user.

MySQL
Login to MySQL
Run Windows Command Shell and execute MySQL command tool,
mysql, with the newly created user and database and supply
password as shown in the following MySQL snapshot to use the tool and
execute SQL Statements:

4.SQL Basics
• Lexical elements
• Data Types
• Literals
• Scalar Expressions
• Query Expressions
• Predicates

Topics
We are going to cover the following topics in this section:
 Lexical Elements
 Data Types
 Literals

Lexical Elements
Tokens, Comments
Simple Latin Letter, Digit, Special Character
Key words, Reserved words, Literals, Identifiers,

Lexical Elements
A Lexical Element is a group of characters of SQL that can
legally appear in an SQL statement.
There are two kinds of lexical elements:
• Tokens
• Comments
A token is a smallest independent unit of the language.
A comment is text ignored by SQL implementations that
process or execute SQL statements. Comments are used for
explaining statements and context of the statements to the
human readers.

SQL Character
As mentioned in earlier slide, lexical elements of SQL
are groups of characters. Each SQL character falls into
one of the following categories:
 simple Latin letter
 digit
 special character

Simple Latin Letter
A simple Latin letter in SQL is
 any upper case Latin letter from A to Z,
 any lower case Latin letter from a to z.

Digit
A digit is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.

Special Character
An SQL special character is a character other than Latin
letters and digits.
SQL special characters are:
“ , ‘, <space>, %, &, *, (, ),
+, -, , , ., :, ;, ?,
<, =, >, [, ], _, |, {, }, ^.

Tokens
Token in SQL is a sequence or group of SQL characters
separated by comments, white space or other SQL special
character.
 A token can be a key word such as SELECT or INSERT.
 A token can be a literal such as 123 or ‘John’.
 A token can be an identifier such as eno or salary.
 A token can be a special character such as ( or =
 and so on…
Each SQL statement is formed of various kinds of tokens.

Key words
A key word in SQL is a reserved word or a non-reserved word.
Reserved words are words such as SELECT, INSERT, AND, OR,
etc., that have special meaning in the language and these can
not be used as identifiers for naming database objects..
Non-reserved words have special meaning only in some specific
contexts and hence can be used as identifiers in other
contexts.
SQL Standard document gives a list of both kinds of key words..

Literals
A literal in SQL is a constant value used in SQL statements.
It can be used for inserting into columns of a table, for
updating existing column values, for comparing with columns
and in various expressions that can be used in SQL statements.
It is represented using SQL characters depending on the data
type it is expected to indicate.
For example, an integer literal is 123 whereas a character
literal is ‘David’.

Comments
There are two types of comments in SQL:
• Simple comment
• Bracketed comment
Simple comment starts with two dashes or minus signs and ends
with a newline character.
Example: -- This is a simple comment.
A bracketed comment starts with /* followed by text of the
comment and ends with */.
Example: /* This is a bracketed
comment. */

Identifiers
SQL Identifiers are used for names of database objects
such as tables, columns and constraints.
 Characters used in identifiers should be in a character
set.
 Default character set consists of A..Z, a..z, 0..9 and _.
 Maximum size of an identifier is 128 characters
 An identifier should start with a letter.
 An identifier can not contain spaces unless delimited by
a pair of double quotes.

Identifiers
Example Valid and Invalid Identifiers
Valid Identifiers Likely use
Employees Name of a table
Salary Name of a column
pk_emp Name of primary key
Warehouse_05 Name of a table
“First Name” A column name
Invalid Identifiers Reason why it is invalid
(Employees) Characters ( and ) are not part of default character set
Employee Salary Spaces in the name
pk-emp Character – is not part of default character set
5th_warehouse Starts with digit

List of SQL Data Types
Data type
category
Data type name Purpose
Boolean BOOLEAN To represent value TRUE or FALSE
Character CHAR
VARCHAR
To represent character data for columns such as
names of persons or cities.
Bit BIT To represent bit 0 or 1 or string of such bits.
Note: Removed from SQL 2003 std.
Exact numeric NUMERIC
DECIMAL
BIGINT
INTEGER
SMALLINT
To represent numbers such as 1, 2, 3, 456 and so
on. It is also used for numbers with fractions such
as 125.68.
Approximate
numeric
FLOAT
REAL
DOUBLE
PRECISION
To represent numbers with fractions such as 125.68
where precision of the fraction may not be
preserved across manipulation of such column
values.

List of SQL Data Types
(contd…)
Data type
category
Data type name Purpose
Datetime DATE
TIME
TIMESTAMP
To represent date, time and timestamp
that contains date and time values.
Interval INTERVAL To represent datetime intervals
Character
large objects
CLOB To represent large amounts of character
data such as resumes, notes, stories and
descriptive text.
Introduced in SQL 2003
Binary large
Objects
BLOB To represent large amounts of binary data
such as photographs, pictures, audio files
and video files.
Introduced in SQL 2003

List of Non-Standard
SQL Data Types
Data type
name
RDBMS Purpose
BINARY
VARBINARY
SQLServer
MySQL
ctreeACE
To represent sequence of arbitrary bytes of data.
SERIAL MySQL Used for serial numbers that are auto incremented.
DATETIME MySQL Same as TIMESTAMP but allows values from a bigger
range.
YEAR MySQL To represent two or four digit year values.
TINYTEXT
MEDIUMTEXT
LONGTEXT
MySQL For CLOB data of various maximum sizes.
TINYBLOB
MEDIUMBLOB
LONGBLOB
MySQL For BLOB data of various maximum sizes.

List of Non Standard
SQL Data Types (Contd)
Data type name RDBMS Purpose
ENUM MySQL To represent a value that is
from a specific set of character
string values.
SET MySQL To represent a set of zero or
more values.
TINYINT MySQL
Ctree-SQL
A one byte integer data type.

More Data Type Terminology
Term Meaning
String data types This term refers to bit or
character data types (CHAR and
VARCHAR)
Numeric data types This term refers to Exact and
Approximate numeric data types.
Large object data types This term refers to CLOB and
BLOB data types

NULL
NULL represents unknown value for relation
attributes/columns.
NULL is used as a value for columns for which data is
unknown at the time of adding a row to a table. It can
also be used as a value for a column at the time of
updating a row and to test if a column in a row is NULL.
NULL cannot be used if a column is defined not to take
NULL values, i.e., the column is defined as a NOT NULL
column, i.e., non-nullabe column.

Syntax Conventions
Symbol Interpretation Example
| Syntax elements separated by
this symbol are alternatives.
BOOLEAN | INTEGER
[ ] An optional syntax element,
i.e., the syntax element need
not be used.
CHAR [(length)]
{ } Used to group tokens together
to indicate contents of the
flower brackets is a one syntax
element.
{CHARACTER | CHAR} [(length)]
... Previous syntax element can
appear zero or more times.
(column-name [, column-name] ...)
The following conventions are used in representing syntax of SQL:

Syntax Conventions (contd)
Textual element Interpretation Examples
Tokens in capital
letters
Key words of SQL.
Case of the letters of the key words
does not matter in actual SQL
statements.
CREATE
INSERT
WHERE
AND
Tokens with one
or more words
in small letters
separated by
hyphen
These represent identifiers, i.e.,
names of database objects or
properties of these objects such as
names of tables, columns and
constraints that need to be
replaced with actual identifiers
while writing SQL statements.
table
table-name
column
column-name
col-list

Data Type BOOLEAN
Values of BOOLEAN column: TRUE or FALSE
Syntax: BOOLEAN
Example: Definition of a column is_manager in a table:
is_manager BOOLEAN

Data Type CHARACTER
Data type CHARACTER or CHAR is used for columns in
which a sequence of characters such as names of
persons, cities, etc., need to be stored.
Syntax: {CHARACTER | CHAR } [(length)]
length: Length of the string. 1 if not specified.
Examples:
book_title CHARACTER(50)
book_category CHAR
Note: CHAR is a fixed-length data type.

Data Type CHAR (contd)
Example column: door_type CHAR(3)
Inserted Value Actual Value Inserted
‘IN’ ‘IN ’
‘OUT’ ‘OUT’
‘INOUT’ Nothing is inserted due
to error.

Data Type VARCHAR
VARCHAR data type means VARYING CHARACTER data
type where size of data stored in such a column in each
row can vary according to the actual size of the data.
If data size is less than the size specified for the column
at the time of its definition, data is not padded with
blanks.
Syntax: { VARCHAR | CHARACTER VARYING |
CHAR VARYING } [ (length) ]
Example:
book_synopsis VARCHAR(500)

Data Type INTEGER
INTEGER data type is used to store integers in the range
of -2147483648 to 2147483647.
Number of bytes occupied in a column by integer is 4
bytes.
Syntax: INTEGER
Examples:
book_sno INTEGER
order_no INTEGER

Data Type SMALLINT
SMALLINT data type is used to store integers in the
range of -32768 to 32767.
Number of bytes occupied in a column by SMALLINT is 2
bytes.
Syntax: SMALLINT
Examples:
roll_no SMALLINT
quantity SMALLINT

Data Type NUMERIC
NUMERIC data type is used to store numbers that can have
fractions.
Syntax: NUMERIC [ ( precision [, scale] ) ]
precision – Total number of digits including number of
decimal places but excluding decimal point.
Default value is RDBMS specific.
scale – Number of decimal places.
Default value is 0.
Examples:
price NUMERIC (8,2)
discount NUMERIC (4,1)
interest NUMERIC (4,2)

NUMERIC Data Type Limits
RDBMS Maximum
Precision
Maximum
Scale
Default
Precision
Default
Scale
MySQL 65 30 10 0
MS SQL Server 38 38 18 0
Ctree ACE 32 32 32 0

Data Type DECIMAL
DECIMAL data type for all practical purposes is same as
NUMERIC data type in most RDBMSs.

Data Type REAL
The REAL data type is an approximate numerical
data type.
Syntax: REAL
Size: 4 bytes
Examples:
salary REAL
width REAL

Data Type FLOAT
The FLOAT data type is an approximate numerical
data type.
Syntax: FLOAT [precision]
precision – This indicates precision of mantissa.
Size: 8 bytes
Examples:
distance FLOAT

Data Type DOUBLE PRECSION
The DOUBLE PRECISION data type is an
approximate numerical data type.
Syntax: DOUBLE PRECISION
Size: 8 bytes
Examples:
distance DOUBLE PRECSION

Datetime Data Types
Datetime data types are used to store points in time in
columns.
Datetime data types are DATE, TIME and TIMESTAMP.
Each datetime data type consists of a meaningful
combination of the following fields:
YEAR, MONTH, DAY,
HOUR, MINUTE, SECOND,
TIMEZONE_HOUR and TIMEZONE_MINUTE.

Data Type DATE
DATE data type is used to store calendar date in columns.
DATE consists of datetime fields:
YEAR, MONTH and DAY.
Syntax: DATE
Examples:
date_of_birth DATE
join_date DATE

DATE Value Ranges
RDBMS Minimum Date Maximum Date
MySQL 1000-01-01 9999-12-31
Oracle 4712-01-01 BCE 4712-12-31 CE
MS SQL Server 1753-01-01
1900-01-01
9999-12-31
2079-06-06
ctreeACE 1700-03-01 9999-12-31

Data Type TIME
TIME data type is used to store time of a day in columns.
TIME consists of datetime fields:
HOUR, MINUTE and SECOND and fields
TIMEZONE_HOUR and TIMEZONE_MINUTE if
WITH TIIMEZONE option is used.
Syntax: TIME [(precision)] [WITH TIMEZONE]
precision: This indicates precision required in seconds value.
Default is 0 which means whole seconds A value 3
means milliseconds and 6 means microseconds
Examples:
start_time TIME
event_time TIME(6)

Data Type TIMESTAMP
TIMESTAMP data type is used to store date and time of a day in
columns.
TIMESTAMP consists of datetime fields: YEAR, MONTH,
DAY, HOUR, MINUTE and SECOND and fields
TIMEZONE_HOUR and TIMEZONE_MINUTE if WITH
TIMEZONE option is used.
Syntax: TIMESTAMP [(precision)] )] [WITH TIMEZONE]
precision: This indicates precision required in seconds
value. Default is 6 which means microseconds.
A value 3 means millisecond .
Examples:
transaction_ts TIMESTAMP
event_ts TIMESTAMP(6)

Data Type CHARACTER LARGE
OBJECT (CLOB))
CHARACTER LARGE OBJECT or CLOB data type is used to
store large amount of character data.
Syntax: { CHARACTER LARGE OBJECT |
CHAR LARGE OBJECT | CLOB
} [ ( large-object-length ) ]
large-object-length: length [ K | M | G ]
[ CHARACTERS | OCTETS ]
length: Length of column in characters.
Examples:
part_description CLOB(5M)
emp_resume CLOB(10K)

Data Type BINARY LARGE
OBJECT (BLOB)
BINARY LARGE OBJECT data type is used to store large
amount of binary data.
Syntax: { BINARY LARGE OBJECT | BLOB }
[ ( large-object-length ) ]
large-object-length: length [ K | M | G ]
Examples:
part_image BLOB(2M)
emp_photograph BLOB(150K)

Literals
A literal is a valid value for an SQL data type that can be inserted
into a column of the data type or existing value of the column can
be updated with the value. It can also be used in expressions to
compare values in columns.
Term constant is synonymous to the term literal.
Example literal values for a column of data type INTEGER could be
1, 2, 3, 596, 123456, etc. A few example literal values for a
CHARACTER column used to store names of employees are ‘Akhil’,
‘Sparsh’ and ‘David’’.

Boolean Literals
Literals of BOOLEAN data type are TRUE and FALSE
Syntax: { true | false }
These literals are case insensitive.

Character Literals
A character literal consists of one or more characters
enclosed in single quotation marks. Character literals can
be used as data for columns of data type CHAR, VARCHAR
and CLOB.
Examples:
‘Mahatma Gandhi’
‘John’
‘Where there is a will there is a way’
Length of a literal that can be used for a column depends
on the length of the column.

INTEGER Literals
INTEGER literals are expressed using numbers having one
or more digits.
An integer literal is any number in the range of
-2147483648 to 2147483647.
Examples:
123
-123
1234567890

SMALLINT Literals
Like an INTEGER literal, a SMALLINT literal is also a
number made up of one or more digits.
A SMALLINT literal is any number in the range of
-32768 to 32767.
Examples:
123
-123
12345

NUMERIC and DECIMAL
Literals
NUMERIC and DECIMAL literals are numbers with
decimal part.
Examples:
20.75
12345.678
The precision and scale depends on the support provided
by the RDBMS product you are using.

Approximate Numeric
Literals
An approximate numeric literal consists of a mantissa and an
exponent. The value of the literal is equivalent to the mantissa
multiplied by 10 to the power of the exponent.
The approximate numeric literal is used to represent values of
data types REAL, FLOAT and DOUBLE PRECISION.
Syntax: mantissa E exponent
mantissa: An exact numeric literal.
exponent: A signed integer.
Examples:
5 E 4 This means 50000
10.2 E 3 This means 10200

DATE Literals
Date literals are specified with key word DATE followed by a
string containing YEAR, MONTH and DAY values.
Syntax: DATE date string
date string: A string containing date in the format
“YYYY-MM-DD”
where YYYY is a four digit year,
MM is a month (1 to 12) and DD is a day of
the month
Examples:
DATE ‘1947-08-15’
DATE ‘2014-01-03’

TIME Literals
Time literals are specified with key word TIME followed by a string
containing HOUR, MINUTE, SECOND and optionally fraction of
second values.
Syntax: TIME time string
time string: A string containing date in the format “HH:MM:SS.F”
where HH is a two digit hour value (0 to 23),
MM is two digit minutes value (0 to 59),
DD is a two digit seconds value (0 to 59) and
F is a fraction usually either 2, 3, 6 or 9 digit value.
Examples:
TIME ‘09:00:25’
TIME ‘14:30:15.123456’

TIMESTAMP Literals
Timestamp literals are specified with key word TIMESTAMP
followed by a date string, a space and time string.
Syntax: TIMESTAMP date string space time string
The date string and time string are as explained in the previous
slides. space is a single blank character.
Examples:
TIMESTAMP ‘1947-08-15 23:59:59’
TIMESTAMP ‘2014-01-03 14:30:15.123456’
Note that you should specify only one space character (blank)
between date and time strings.

BINARY String Literals
Binary String Literals are used to store data in columns of
data type BLOB, BINARY or VARBINARY columns. A
Binary Literal consists of one or more pairs of
hexadecimal digits enclosed in a pair of single quotes
prefixed by letter X.
Syntax: X ‘{hexit hexit}…’
hexit: A hexadecimal digit which is a digit or any
of the letters A to F or a to f.
Examples:
X ‘ABCD’
X ‘a12bc2d4’

 Lexical Elements of SQL
 Tokens and Comments
 SQL Character
 Simple Latin Letters, Digits and Special Characters
 Key words – reserved words and non-reserved words
 Literals
 Simple and Bracketed comments
 Identifiers
 SQL Data Types
 NULL
 Literals for each Data Type

Database Systems - Introduction to SQL (Chapter 3/1)

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Database Systems - Introduction to SQL (Chapter 3/1)