Corrected Introduction to database slide

2.  In our programs we use variables to store
information.
 But when our program terminates all the
variables declared in it disappear.
 Why this happens????

3.  What if we need some information to be
stored even after the termination of
program. (We are here in this session for
this need).
 How can we fulfill this need?
 Any suggestion……..

4.  The most simple solution is store the
information in the disk.
 Now the question is how we can store in
disk.
 Create a file and store there.(simple
enough)
 Is it a good solution or the best solution ?

6.  Suppose we want to implement the log in
section.(feature 1)
 We use a file and store the user_id and
password in the following manner

7.  When 1105120 wants to log in we have to
check all the previous record.
 Also we have to check whether multiple
users are accessing the file.
 Any more problem………….

8.  So we need to care about a lot of facts
beside storing, updating the file.
 But we are lazy people. We always want to
minimize our task.(At least me!)
 Thank GOD there are some applications or
Systems which handle the facts about
which we were worried 

9.  And
they are called DataBase
Management System(DBMS).
• Oracle
• IBM DB2
• Microsoft SQL Server
• Microsoft Access
• PostgreSQL
• MySQL
• SQLite

10.  But not all our problems have been solved.

 Why???
 Because now we have to learn how to
maintain Database using DBMS .
 Here we will see how to manage database
using MySQL.

11.  CREATE DATABASE [IF NOT EXISTS]
database_name;
 Example: Suppose I want to create a
database named “Quiz”.
 So the query will be
CREATE DATABASE IF NOT EXISTS QUIZ;

12.  SHOW DATABASES;
 You will see something like this-

13.  DROP DATABASE [IF EXISTS]
database_name;
 Example : Suppose I want to delete the
quiz database :
 So the query will be
DROP DATABASE IF EXISTS Quiz;

15.  We have created Database in MySQL.
 Now we will store data in Database.
 We store data in Tabular format in MySQL.
 That means we have to create tables to
store data.

16.  CREATE TABLE [IF NOT EXISTS]
table_name( column_list
) type=table_type
Example: Suppose I want to create table
named “User_Password”

17. Query will be:
CREATE TABLE USER_PASSWORD(
username varchar(6),
password varchar(6)
);
Username(varchar(6)) Password(varchar(6))

18.  To
see the created table in the database
use query
SHOW TABLES;
 To
see the description of a particular table
use query
DESCRIBE table_name;

19.  INSERT INTO tbl_name () VALUES();
 Example:
• INSERT INTO USER_PASSWORD
VALUES(„0705001‟,‟123456‟);
• INSERT INTO USER_PASSWORD
VALUES(„0705002‟,‟678901‟);
Username(varchar(6)) Password(varchar(6))
0705001 123456
0705002 678901

20.  Alter table is used to change the structure
of the table
 Suppose we forgot to add a column in the
USER_PASSWORD table.
 Now we want to add a column name „type‟
in that table

21.  ALTER
TABLE USER_PASSWORD
ADD COLUMN TYPE VARCHAR(5);
Using ALTER TABLE query:
• We can also drop column
• Rename the table
• Change the properties of a column

22.  SELECT column_name1,column_name2...
FROM tables [WHERE conditions]
[GROUP BY group [HAVING
group_conditions]] [ORDER BY
sort_columns] [LIMIT limits];
 Looking very complex 

23.  Mostsimple select statement
 SELECT * FROM table_name;
• It selects the whole table;
 SELECT COLUMN_NAME FROM TABLE
• Example:
SELECT USERNAME,TYPE FROM
USER_PASSWORD;

24.  We do not always want to select the whole
table .Most of the time part of a table.
 Example:
• SELECT PASSWORD,TYPE FROM
USER_PASSWORD WHERE USERNAME =
„0705001‟;

25.  Primary key is used to distinguish two rows
in a table.
 Now if I execute
INSERT INTO USER_PASSWORD
VALUES(„0705001‟,‟hello‟);
Username(varchar(6)) Password(varchar(6))
0705001 123456
0705001 hello
0705002 678901

26.  Big problem.
 One user two passwords. :O
 We can avoid it by making USERNAME
column as primary key.
 By making USERNAME column a primary
key we ensure that this column will have
all distinct value.

27. CREATE TABLE USER_PASSWORD(
username varchar(6),
password varchar(6),
PRIMARY KEY (USERNAME)
);

28.  Used to change data in the table.
 UPDATE table_name SET column_name
=
value WHERE (Some condition is true);
Suppose 0705001 wants to change his/her
password. The query will be :
UPDATE USER_PASSWORD SET
PASSWORD = „1234‟ WHERE
USERNAME = „0705001‟;

29.  Usedto delete data in the table.
 DELETE FROM table_name WHERE
(Some condition is true);
Suppose we want to throw out an
user(0*0*200) from our Database !!!
DELTE FROM USER_PASSWORD
WHERE USERNAME = „0*0*200‟;

30.  These were very basic database queries.
 Don‟t be worried if you did not understand
all the topics.
 You will learn all this and many other
features in 3-1.

31. THANK YOU