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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
A Guide to MySQL9
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
A Guide to MySQL27
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
A Guide to MySQL28
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
A Guide to MySQL38
Correcting Errors in the Database
• UPDATE: change the value in a table• DELETE: delete a row from a table
A Guide to MySQL39
Correcting Errors in the Database (continued)
A Guide to MySQL40
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
A Guide to MySQL42
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
A Guide to MySQL43
Creating the Remaining Database Tables
• Execute appropriate CREATE TABLE and INSERT commands
• Save these commands to a secondary storage device
A Guide to MySQL44
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