Mysql Informational Document

7/31/2019 Mysql Informational Document

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Introduction to Databases

Client-serverInstalling Mysql


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What are databases

A database is a collection of related data

It represents some aspects of the real world.

It is a logically coherent collection of data.

It is designed for specific purpose and intended users.

It can be at varying size and complexity

It can be generated and maintained manually


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What are databases

A database managementsystem (DBMS) consistsof these components:

Database applicationsare often built on aclient-server model.

Stored databasedefinitions (meta-

data)

Software to access stored data

Software to process queries

Application programs/queries

DBMSsoftware

DBMS

system

Stored database

Users/Programmers

clients

server


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The clients and the server

Source: http://infomotions.com/musings/waves/clientservercomputing.html


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The clients and the server

The client's responsibility includes:

1. Handle the user interface.

2. Translate the user's request into

the desired protocol.3. Send the request to the server.

4. Wait for the server's response.

5. Translate the response into"human-readable" results.

6. Present the results to the user.

The server's functions include:

1. Listen for a client's query.

2. Process that query.

3.

Return the results back tothe client.

Source: http://infomotions.com/musings/waves/clientservercomputing.html


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Database client: Interfacing (input)

Example: When you go to the NVCC library to do an article search

This is the

interface thatallows user tospecify thesearch criteria:


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Database client: Interfacing (input)


Search for mysql as a keyword anywhere in

the Northern Virginia CC database, in alllanguages and in all years, and in all formats


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Database client: Communicationwith the server


Client converts the informationto a database query language

and send to the server (usuallyacross the internet)

Search for mysql as a keyword anywhere in

the Northern Virginia CC database, in alllanguages and in all years, and in all formats

SELECT * FROM Northern_Virginia_CC_database

WHERE keyword=mysql

This is the actual stuff being sent out to the DBMS to do the search

This is what the user means to find:


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Database client: Interfacing (output)


Server returnsa list of resultsto the client.

The clientdisplays the

results in ahuman-friendlyformat


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Database client: Interfacing (output)


The clientdisplays thedetails of arecord in thesearch result ina human-friendly format


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The whole process of a databasequery


User enterssearch criteria

Database managementsystem at the server

Client displays

search resultto the user

SELECT * FROM

Northern_Virginia_CC_database

WHERE keyword=mysql

Client convertssearch criteria to aquery and sends it tothe server

We are going tolook at the thingshappening at theserver behind the

scene here.


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Mysql

A freeware

Two main components:

The server (called mysql-server) The client (called mysql-client)

We are interested primarily in the server.


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How to install mysql-server inubuntu (internet required)

If you have installed ubuntu, this is pretty straightforward:

1. Open a terminal by pressing Ctrl-Alt-T (on a windows keyboard) orCtrl-Option-T (on a mac keyboard)

2. Type: sudo apt-get install mysql-server

You will need to enter the administrater password (that is thepassword for your ubuntu account) to do this installation.

https://help.ubuntu.com/11.04/serverguide/C/mysql.html

A video to show how to install mysql-server in ubuntu:

http://www.youtube.com/watch?v=bt2jACLDLmE
https://help.ubuntu.com/11.04/serverguide/C/mysql.htmlhttps://help.ubuntu.com/11.04/serverguide/C/mysql.html


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Useful tools on ubuntu

To open a terminal:Open a terminal by pressing Ctrl-Alt-T (on a windows

keyboard) or Ctrl-Option-T (on a mac keyboard)

To edit a text file:

pico (In pico, the symbol ^ means the controlkey. So ^G means control-G)

For more advanced users: vi


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Databases in Mysql

To show, create, use and drop databases:

To show all the databases accessible to you:show databases;

To create a database called cars:create database cars;

To use the database called cars:use cars;

To drop a database called cars:drop database cars;

All commands endwith semicolon ;


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Getting mysql

At the ubuntu xterm prompt, type:

sudo apt-get install mysql-server

.


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Starting mysql

At the ubuntu xterm prompt: mysql -u root (require password)

You will see the prompt:mysql>

.


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Show all databases

To see the databases on the server, type command:

show databases;

These three are default databases.There is nothing else.


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Create a database

To create a database called fruits on the server, type command:

create database fruits;

There is now one more database,

called fruits.


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Use a database (must be created already)

To use the database called fruits that is already created on theserver, type command:

use fruits;

You can use the following command to see what is inside the fruitsdatabase:

show tables;

There is nothing in the fruitsdatabase.


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Create a table within adatabase

A database is a collection of tables.

Example: A database about fruits

Nutritiontable

Fruits database

CultivationtableRecipe

table

The nutrition table may containthe following information:

Fruit name, Calories per fruit, Sugar per fruit, Vitamin A content, Vitamin C content,


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Create a table within adatabase

A database is a collection of tables. To create a new table callednutrition in the fruit database, type command:

create table nutrition (name varchar(20),

calories int, sugar int, vitaminA int, vitamic

int);

There is now one table in the fruitsdatabase.


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To see the description of a table

To see the description of the nutrition table in the fruit database,type command:

describe nutrition;

There are 5 fields in thenutrition table.


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To insert an entry into a table

Suppose we have the following information about thenutrition of apple and we want to insert an entry it intothe nutrition table of the database.

Apple (one fruit) contains:

95 Calories

19g of sugars

2% of an adults daily need of vitamin A 14% of an adults daily need of vitamin C


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To insert an entry into a table

This command insert an entry called apple into the table:

insert into nutrition values(apple, 95, 19, 2, 14);

You can span yourcommand over multiplelines. It is terminated only bythe semicolon ;


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To see all entries in a table

This command shows all the entries in the nutrition table:

select * from nutrition;

The nutrition table has onlyone entry, which is apple.

The * means everything.


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Entering data into the database

There are a few ways to enter data into a table of adatabase.

Entering one entry at a time

Loading a whole file of entries

Suppose you want to enter large quantity of data, youmay have the data stored in a file, and then load it into

mysql. We are going to show how to do that. First, you must quit mysql.

Then you can use pico to edit the file.

You can load the file in mysql when you are done.


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To quit an interactive sessionwith mysql

To quit an interactive session with the mysql server, typecommand:

quit;

Now the prompt changes back to the linux xterm prompt.


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To edit a file of data entries

You can edit a file of data entries using pico. The data file needs tofollow this format:

One data entry per line

Each field must be separated by a tab

Do not leave any empty lines after the

last line. Make sure your cursor cannotmove past here when you are done.

Name this file: fruit-nutrition.txt


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Permanence of data in thedatabase

Data entered into a database arepermanent. If you quit now, and come

back later, you can still see the data. Now let us return to mysql to see that.


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To return to mysql

To return to mysql, type:mysql -u root

Then, we can type use fruits, and then check the table.

Once inside mysql, we canuse these commands tocheck the database

We can see that

the nutrition tableis still there, andthe apple entry isstill in the table.


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Adding and deleting data in atable

Suppose we want to delete all the existing datain the nutrition table, and then load the tablewith the data from the file called fruit-nutrition.txtthat we created.

We need to do this in two steps.

First, delete existing entries in the table.

Second, load the data from the file into the table.


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Deleting data in a table

To delete all data entries from the nutrition table, type command:

delete from nutrition;

We can see that the nutrition

table is now empty.


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Loading a file of data into atable

To load a file (called fruit-nutrition.txt) of data entries into the nutrition table, typecommand:

load data local infile fruit-nutrition.txt into table

nutrition;

We can see that

the nutrition tableis now loadedwith data fromthe file.


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To add an entry into an existingtable

This command insert an entry called aple into the table:

insert into nutrition values(aple, 95, 19, 2, 14);

(Note: the name aple is an intentional misspell of apple)

The newentry is atthe bottom


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To update an entry in anexisting table

There are a few ways to correct or update adata entry in the table:

Delete the entry and enter a new one

Change the field of an entry


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To delete an entry in an existingtable

This command deletes the entry aple from the nutrition table:

delete from nutrition where name=aple;

The aple

entry is gone.


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To reinsert an entry into a table

This command insert a new entry of apple into the table:

insert into nutrition values(apple, 95, 19, 2, 14);

The new entryof apple entry

is added.


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To change the field of an entryin a table

This command changes the vitaminC field of apple from 14 to 20:

update nutrition set vitaminC=20 where name=apple;

The new valueof applesvitaminC filedis 20.


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To display selected fields

This command displays the fruits by their names and vitaminCcontents, in sorted order of the vitaminC field:

Select name, vitaminC from nutrition order by vitaminC;


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To select fields with constraints

This command select the names of those fruits that have theirvitaminC fields greater than value 100:

Select name from nutrition where vitaminC>100;


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More tutorials on mysql

For more examples on mysql see:

MySQL 5.6 Reference Manual: Chapter 3 Tutorial

http://dev.mysql.com/doc/refman/5.6/en/tutorial.html
http://dev.mysql.com/doc/refman/5.6/en/tutorial.htmlhttp://dev.mysql.com/doc/refman/5.6/en/tutorial.html

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