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Transcript
3 A Guide to MySQL 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 MySQL 2 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 MySQL 3 Objectives (continued) • Save SQL commands and results to a file • Describe a table’s layout using MySQL A Guide to MySQL 4 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 MySQL 5 Introduction to MySQL • Starting MySQL • Obtaining help • Accessing the MySQL Reference Manual A Guide to MySQL 6 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 MySQL 7 Obtaining Help in MySQL • Type \h at MySQL> prompt • Type “help” followed by name of command – help contents – help union A Guide to MySQL 8 A Guide to MySQL 9 Using MySQL Reference Manual to Get Help • Click MySQL Manual - Table of Contents on MySQL 4.1 submenu • Can access online A Guide to MySQL 10 A Guide to MySQL 11 Creating a Database • Must create a database before creating tables • Use CREATE DATABASE command • Include database name A Guide to MySQL 12 Creating a Database (continued) A Guide to MySQL 13 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 MySQL 14 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 MySQL 15 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 MySQL 16 Creating the REP Table A Guide to MySQL 17 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 MySQL 18 Running SQL Commands A Guide to MySQL 19 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 MySQL 20 Errors in SQL Commands A Guide to MySQL 21 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 MySQL 22 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 MySQL 23 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 MySQL 24 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 MySQL 25 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 MySQL 26 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 MySQL 27 The Insert Command A Guide to MySQL 28 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 MySQL 29 Adding Additional Rows A Guide to MySQL 30 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 nonnull values, then list only the non-null values after the VALUES command A Guide to MySQL 31 The INSERT Command with Nulls • Enter only non-null values • Precisely indicate values you are entering by listing the columns A Guide to MySQL 32 The INSERT Command with Nulls (continued) A Guide to MySQL 33 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 MySQL 34 Viewing Table Data (continued) A Guide to MySQL 35 Viewing Table Data (continued) A Guide to MySQL 36 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 MySQL 37 Correcting Errors in the Database • UPDATE: change the value in a table • DELETE: delete a row from a table A Guide to MySQL 38 Correcting Errors in the Database (continued) A Guide to MySQL 39 Correcting Errors in the Database (continued) A Guide to MySQL 40 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 MySQL 41 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 MySQL 42 Creating the Remaining Database Tables • Execute appropriate CREATE TABLE and INSERT commands • Save these commands to a secondary storage device A Guide to MySQL 43 Describing a Table A Guide to MySQL 44 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 MySQL 45 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 MySQL 46 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 MySQL 47 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 A Guide to MySQL 48