A Guide to MySQL

3

A Guide to MySQL2

Objectives

• Start MySQL and learn how to use the MySQL Reference Manual

• Create a database

• Change (activate) a database

• Create tables using MySQL

• Create and run SQL commands in MySQL

A Guide to MySQL3

Objectives (continued)

• Identify and use data types to define columns in tables

• Understand and use nulls

• Add rows to tables

• View table data

• Correct errors in a database

A Guide to MySQL4

Objectives (continued)

• Save SQL commands and results to a file

• Describe a table’s layout using MySQL

A Guide to MySQL5

Introduction

• Structured Query Language (SQL):

– Popular and widely used language for retrieving and manipulating database data

– Developed in mid-1970s under the name SEQUEL

– Renamed SQL in 1980

– Used by most DBMSs

A Guide to MySQL6

Introduction to MySQL

• Starting MySQL

• Obtaining help

• Accessing the MySQL Reference Manual

A Guide to MySQL7

Starting MySQL

• Windows XP– Click Start button

– Point to All Programs

– Point to MySQL on menu

– Point to MySQL Server 4.1

– Click MySQL Command Line Client • Must enter password in Command Line Client

window

A Guide to MySQL8

Obtaining Help in MySQL

• Type \h at MySQL> prompt

• Type “help” followed by name of command

– help contents

– help union

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A Guide to MySQL10

Using MySQL Reference Manual to Get Help

• Click MySQL Manual - Table of Contents on MySQL 4.1 submenu

• Can access online

A Guide to MySQL11

A Guide to MySQL12

Creating a Database

• Must create a database before creating tables

• Use CREATE DATABASE command

• Include database name

A Guide to MySQL13

Creating a Database (continued)

A Guide to MySQL14

Changing the Default Database

• Default database: database to which all subsequent commands pertain

• USE command, followed by database name:– Changes the default database

– Execute at the start of every session

A Guide to MySQL15

Creating a Table• Describe the layout of each table in the database

• Use CREATE TABLE command

• TABLE is followed by the table name

• Follow this with the names and data types of the columns in the table

• Data types define type and size of data

A Guide to MySQL16

Table and Column Name Restrictions

• Names cannot exceed 18 characters

• Must start with a letter

• Can contain letters, numbers, and underscores (_)

• Cannot contain spaces

A Guide to MySQL17

Creating the REP Table

A Guide to MySQL18

Entering Commands in MySQL

• Commands are free-format; no rules stating specific words in specific positions

• Press ENTER to move to the next line in a command

• Indicate the end of a command by typing a semicolon

• Commands are not case sensitive

A Guide to MySQL19

Running SQL Commands

A Guide to MySQL20

Editing SQL Commands

• Statement history: stores most recently used command

• Editing commands:– Use arrow keys to move up, down, left, and right– Use Ctrl+A to move to beginning of line– Use Ctrl+E to move to end of line– Use Backspace and Delete keys

A Guide to MySQL21

Errors in SQL Commands

A Guide to MySQL22

Editing MySQL Commands

• Press Up arrow key to go to top line

• Press Enter key to move to next line if line is correct

• Use Right and Left arrow keys to move to location of error

• Press ENTER key when line is correct

• If Enter is not pressed on a line, line not part of the revised command

A Guide to MySQL23

Dropping a Table

• Can correct errors by dropping (deleting) a table and starting over

• Useful when table is created before errors are discovered

• Command is followed by the table to be dropped and a semicolon

• Any data in table also deleted

A Guide to MySQL24

Data Types• For each table column, type of data must be defined

• Common data types:

– CHAR(n)

– VARCHAR(n)

– DATE

– DECIMAL(p,q)

– INT

– SMALLINT

A Guide to MySQL25

Nulls

• A special value to represent situation when actual value is not known for a column

• Can specify whether to allow nulls in the individual columns

• Should not allow nulls for primary key columns

A Guide to MySQL26

Implementation of Nulls

• Use NOT NULL clause in CREATE TABLE command to exclude the use of nulls in a column

• Default is to allow null values

• If a column is defined as NOT NULL, system will reject any attempt to store a null value there

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Adding Rows to a Table

• INSERT command:

– INSERT INTO followed by table name

– VALUES command followed by specific values in parentheses

– Values for character columns in single quotation marks

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The Insert Command

A Guide to MySQL29

Modifying the INSERT Command

• To add new rows modify previous INSERT command

• Use same editing techniques as those used to correct errors

A Guide to MySQL30

Adding Additional Rows

A Guide to MySQL31

The INSERT Command with Nulls

• Use a special format of INSERT command to enter a null value in a table

• Identify the names of the columns that accept non-null values, then list only the non-null values after the VALUES command

A Guide to MySQL32

The INSERT Command with Nulls

• Enter only non-null values• Precisely indicate values you are entering by listing

the columns

A Guide to MySQL33

The INSERT Command with Nulls (continued)

A Guide to MySQL34

Viewing Table Data

• Use SELECT command to display all the rows and columns in a table

• SELECT * FROM followed by the name of the table

• Ends with a semicolon

A Guide to MySQL35

Viewing Table Data (continued)

A Guide to MySQL36

Viewing Table Data (continued)

A Guide to MySQL37

Correcting Errors In the Database

• UPDATE command is used to update a value in a table

• DELETE command allows you to delete a record

• INSERT command allows you to add a record

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Correcting Errors in the Database

• UPDATE: change the value in a table• DELETE: delete a row from a table

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Correcting Errors in the Database (continued)

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Correcting Errors in the Database (continued)

A Guide to MySQL41

Saving SQL Commands

• Allows you to use commands again without retyping

• Different methods for each SQL implementation you are using

– Oracle SQL*Plus and SQL*Plus Worksheet use a script file

– Access saves queries as objects

– MySQL uses an editor to save text files

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Saving SQL Commands

• Script file:– File containing SQL commands

– Use a text editor or word processor to create

– Save with a .txt file name extension

– Run in MySQL:• SOURCE file name

• \. file name

– Include full path if file is in folder other than default

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Creating the Remaining Database Tables

• Execute appropriate CREATE TABLE and INSERT commands

• Save these commands to a secondary storage device

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Describing a Table

A Guide to MySQL45

Summary

• Use MySQL Command Line Client window to enter commands

• Type \h or help to obtain help at the mysql> prompt• Use MySQL Reference Manual for more detailed

help

A Guide to MySQL46

Summary (continued)

• Use the CREATE DATABASE command to create a database

• Use the USE command to change the default database

• Use the CREATE TABLE command to create tables

• Use the DROP TABLE command to delete a table

A Guide to MySQL47

Summary (continued)

• CHAR, VARCHAR, DATE, DECIMAL, INT and SMALLINT data types

• Use INSERT command to add rows• Use NOT Null clause to identify columns that cannot

have a null value• Use SELECT command to view data in a table

A Guide to MySQL48

Summary (continued)

• Use UPDATE command to change the value in a column

• Use DELETE command to delete a row• Use SHOW COLUMNS command to display a

table’s structure