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MySQL Tutorial
Introduction to Database

Introduction of MySQL
• MySQL is an SQL (Structured Query Language) based
relational database management system (DBMS)
• MySQL is compatible with standard SQL
• MySQL is frequently used by PHP and Perl
• Commercial version of MySQL is also provided (including
technical support)

Resource
• MySQL and GUI Client can be downloaded
from
http://dev.mysql.com/downloads/

• The SQL script for creating database ‘bank’
can be found at
– http://www.cs.kent.edu/~mabuata/DB10_lab/bank_db.sql

Command for accessing MySQL
• Access from DB server
>ssh dbdev.cs.kent.edu
Start MySQL
>mysql –u [username] –p
>Enter password:[password]

• From a departmental machine
>mysql -u [username] -h dbdev.cs.kent.edu –p
>Enter password:[password]

Entering & Editing commands
• Prompt mysql>
– issue a command
– Mysql sends it to the server for execution
– displays the results
– prints another mysql>

• a command could span multiple lines
• A command normally consists of SQL
statement followed by a semicolon

Command prompt
prompt

meaning

mysql>

Ready for new command.

->

Waiting for next line of multiple-line command.

‘>

Waiting for next line, waiting for completion of a
string that began with a single quote (“'”).

“>

string that began with a double quote (“"”).

`>

Waiting for next line, waiting for completion of an
identifier that began with a backtick (“`”).

/*>

comment that began with /*.

MySQL commands
•
•
•
•
•

help h
Quit/exit q
Cancel the command c
Change database use
…etc

Info about databases and tables
• Listing the databases on the MySQL server host
– >show databases;

• Access/change database
– >Use [database_name]

• Showing the current selected database
– > select database();

• Showing tables in the current database
– >show tables;

• Showing the structure of a table
– > describe [table_name];

Banking Example
branch (branch-name, branch-city, assets)
customer (customer-name, customer-street, customer-city)
account (account-number, branch-name, balance)
loan (loan-number, branch-name, amount)
depositor (customer-name, account-number)
borrower (customer-name, loan-number)
employee (employee-name, branch-name, salary)

CREATE DATABASE
• An SQL relation is defined using the CREATE DATABASE
command:
– create database [database name]

• Example
– create database mydatabase

SQL Script for creating tables
• The SQL script for creating database ‘bank’
can be found at
http://www.cs.kent.edu/~mabuata/DB10_lab/bank_db.sql
http://www.cs.kent.edu/~mabuata/DB10_lab/bank_data.sql

Notice: we do not have permission to create database,
so you have to type command “use [your_account]” to
work on your database.

Query
•

To find all loan number for loans made at the Perryridge branch with loan
amounts greater than $1100.
select loan_number from loan
where branch_name = ‘Perryridge’ and amount>1100;

•

Find the loan number of those loans with loan amounts between $1,000
and $1,500 (that is, ≥$1,000 and ≤$1,500)
select loan_number from loan
where amount between 1000 and 1500;

Query
Find the names of all branches that have greater assets than some branch located
in Brooklyn.
select distinct T.branch_name
from branch as T, branch as S
where T.assets > S.assets and S.branch_city = ‘Brooklyn’;
Find the customer names and their loan numbers for all customers having a loan
at some branch.
select customer_name, T.loan_number, S.amount
from borrower as T, loan as S
where T.loan_number = S.loan_number;

Set Operation
•

Find all customers who have a loan, an account, or both:
(select customer_name from depositor)
union
(select customer_name from borrower);

•

Find all customers who have an account but no loan.
(no minus operator provided in mysql)
select customer_name from depositor
where customer_name not in
(select customer_name from borrower);

Aggregate function
•

Find the number of depositors for each branch.
select branch_name, count (distinct customer_name)
from depositor, account
where depositor.account_number = account.account_number
group by branch_name;

•

Find the names of all branches where the average account balance is more than
$500.
select branch_name, avg (balance)
from account
group by branch_name
having avg(balance) > 500;

Nested Subqueries
•

Find all customers who have both an account and a loan at the bank.
select distinct customer_name
from borrower
where customer_name in
(select customer_name from depositor);

•

Find all customers who have a loan at the bank but do not have an
account at the bank
select distinct customer_name
from borrower
where customer_name not in
(select customer_name from depositor);

Nested Subquery
•

Find the names of all branches that have greater assets than all branches
located in Horseneck.
select branch_name
from branch
where assets > all
(select assets
from branch
where branch_city = ‘Horseneck’);

Create View (new feature in mysql 5.0)
•

A view consisting of branches and their customers
create view all_customer as
(select branch_name, customer_name
from depositor, account
where depositor.account_number = account.account_number)
union
(select branch_name, customer_name
from borrower, loan
where borrower.loan_number=loan.loan_number);

Joined Relations
•
•
•
•

Join operations take two relations and return as a result another relation.
These additional operations are typically used as subquery expressions in the
from clause
Join condition – defines which tuples in the two relations match, and what
attributes are present in the result of the join.
Join type – defines how tuples in each relation that do not match any tuple in
the other relation (based on the join condition) are treated.

Joined Relations – Datasets for Examples
•

Relation loan

Relation borrower

Note: borrower information missing for L-260 and loan
information missing for L-155

Joined Relations – Examples

• Select * from loan inner join borrower on
loan.loan-number = borrower.loan-number
loan-number

branch-name

amount

customer-name

loan-number

L-170

Downtown

3000

Jones

L-170

L-230

Redwood

4000

Smith

L-230

Example

Select * from loan left join borrower on
loan.loan-number = borrower.loan-number
loan-number

branch-name

amount

customer-name

loan-number

L-170

Downtown

3000

Jones

L-170

L-230

Redwood

4000

Smith

L-230

L-260

Perryridge

1700

null

null

Modification of Database
•

Increase all accounts with balances over $800 by 7%, all other accounts
receive 8%.
update account
set balance = balance ∗ 1.07
where balance > 800;
update account
set balance = balance ∗ 1.08
where balance ≤ 800;

•

Increase all accounts with balances over $700 by 6%, all other accounts
receive 5%.
update account
set balance =case
when balance <= 700 then balance *1.05
else balance * 1.06
end;

•

Delete the record of all accounts with balances below the average at the
bank.
delete from account
where balance < (select avg (balance) from account);

•

Add a new tuple to account
insert into account
values (‘A-9732’, ‘Perryridge’,1200);

Exercise

1.Create a database employee and create a
table employee in it and do insert delete
updating operation on data

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