MySQL 指南

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
 http://www.cs.kent.edu/~mabuata/DB10_lab/bank_data.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 (“'”).
“> Waiting for next line, waiting for completion of a
string that began with a double quote (“"”).
`> Waiting for next line, waiting for completion of an
identifier that began with a backtick (“`”).
/*> Waiting for next line, waiting for completion of a
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
branch-name amount
Downtown
Redwood
3000
4000
customer-name loan-number
Jones
Smith
L-170
L-230
loan-number
L-170
L-230

Example
 Select * from loan left join borrower on
loan.loan-number = borrower.loan-number
branch-name amount
Downtown
Redwood
Perryridge
3000
4000
1700
customer-name loan-number
Jones
Smith
null
L-170
L-230
null
loan-number
L-170
L-230
L-260

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);

MySQL 指南

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