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PHP and MySQL Database
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Connecting to MySQL Note: you need to make sure that you have MySQL software properly installed on your computer before you attempt to make a connection. You also need to have a user name and password. Syntax for connecting to a database is: $dbc = mysql_connect (‘localhost’, ‘username’, ‘password’); Once you are done working with the DB close the connection: mysql_close();
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PHP Script to Test Database Connection <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Connect to MySQL <?php // Script 12.1 - mysql_connect.php (This script connects to the MySQL server). // Address error handling. ini_set ('display_errors', 1); error_reporting (E_ALL & ~E_NOTICE); // Attempt to connect to MySQL and print out messages. if ($dbc = mysql_connect ('localhost', 'username', 'password')) { print ' Successfully connected to MySQL. '; mysql_close(); // Close the connection. } else { print ' Could not connect to MySQL. '; } ?>
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MySQL Error Handling Common errors you will encounter are: Failure to connect to MySQL Failure in selecting a database Inability to run a query No results being returned by a query Data not being inserted into a table Using mysql_error() function returns a textual version of the error that the MySQL server returned: Die (‘ Could not connect to MySQL because: ’. Mysql_error(). ‘ ’);
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Creating and Selecting a Databse To create a database with PHP use: mysql_query(‘CREATE DATABASE mydatabase’); To select the database use: Mysql_select_db(‘mydatabase’);
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PHP Code to Create and Select a DB <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Create the Database <?php // Script 12.3 - create_db.php (This script connects to the MySQL server. It also creates and selects the database. // Address error handling. ini_set ('display_errors', 1); error_reporting (E_ALL & ~E_NOTICE); // Attempt to connect to MySQL and print out messages. if ($dbc = @mysql_connect ('localhost', 'username', 'password')) { print ' Successfully connected to MySQL. '; if (@mysql_query ('CREATE DATABASE myblog')) { print ' The database has been created. '; }
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Continued else { die (' Could not create the database because: '. mysql_error(). ' '); } if (@mysql_select_db ('myblog')) { print ' The database has been selected. '; } else { die (' Could not select the database because: '. mysql_error(). ' '); } mysql_close(); // Close the connection. } else { die (' Could not connect to MySQL because: '. mysql_error(). ' '); } ?>
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Creating a Table <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Create a Table <?php // Script 12.4 - create_table.php (This script connects to the MySQL server, selects the database, and creates a table). // Address error handling. ini_set ('display_errors', 1); error_reporting (E_ALL & ~E_NOTICE); // Connect and select. if ($dbc = @mysql_connect ('localhost', 'username', 'password')) { if (!@mysql_select_db ('myblog')) { die (' Could not select the database because: '. mysql_error(). ' '); } else { die (' Could not connect to MySQL because: '. mysql_error(). ' '); }
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Continued // Define the query. $query = 'CREATE TABLE blog_entries (blog_id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, title VARCHAR(100) NOT NULL, entry TEXT NOT NULL, date_entered DATETIME NOT NULL )'; // Run the query. if (@mysql_query ($query)) { print ' The table has been created. '; } else { die (' Could not create the table because: '. mysql_error(). '. The query being run was: '. $query. ' ');} mysql_close(); // Close the connection. ?>
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Inserting Data into a DB <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Add a Blog Entry <?php // Script 12.5 - add_entry.php (This script adds a blog entry to the database). // Address error handling. ini_set ('display_errors', 1); error_reporting (E_ALL & ~E_NOTICE); if (isset ($_POST['submit'])) { // Handle the form. // Connect and select. if ($dbc = @mysql_connect ('localhost', 'username', 'password')) { if (!@mysql_select_db ('myblog')) { die (' Could not select the database because: '. mysql_error(). ' '); } else { die (' Could not connect to MySQL because: '. mysql_error(). ' '); }
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Continued // Define the query. $query = "INSERT INTO blog_entries (blog_id, title, entry, date_entered) VALUES (0, '{$_POST['title']}', '{$_POST['entry']}', NOW())"; // Execute the query. if (@mysql_query ($query)) { print ' The blog entry has been added. '; } else { print " Could not add the entry because: ". mysql_error(). ". The query was $query. "; } mysql_close(); } // Display the form. ?> Entry Title: Entry Text:
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Retrieving Data from a Database Retrieved information must be assigned to a variable: $query = ‘SELECT * FROM tablename’; You may use the WHERE clause to restrict which records to be retrieved:$query = ‘SELECT Lname, Fname FROM employees WHERE (dept = ‘sales’);
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Retrieving Table Information <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> View My Blog <?php // Script 12.6 - view_blog.php // This script retrieves blog entries from the database. // Address error handling. ini_set ('display_errors', 1); error_reporting (E_ALL & ~E_NOTICE); // Connect and select. if ($dbc = @mysql_connect ('localhost', 'username', 'password')) { if (!@mysql_select_db ('myblog')) { die (' Could not select the database because: '. mysql_error(). ' ');}} else { die (' Could not connect to MySQL because: '. mysql_error(). ' ');} // Define the query. $query = 'SELECT * FROM blog_entries ORDER BY date_entered DESC'; if ($r = mysql_query ($query)) {
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Code Continued // Run the query. // Retrieve and print every record. while ($row = mysql_fetch_array ($r)) { print " {$row['title']} {$row['entry']} Edit Delete \n";}} else { // Query didn't run. die (' Could not retrieve the data because: '. mysql_error(). ". The query was $query. ");} // End of query IF. mysql_close(); // Close the database connection. ?>
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Deleting Data The syntax is: DELETE FROM tablename WHERE column=value LIMIT 1; Function mysql_affected_rows() returns the number of rows affected by an insert, delete or update query.
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Deleting Table Information <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Delete a Blog Entry <?php // Script 12.7 - delete_entry.php // This script deletes a blog entry. // Address error handling. ini_set ('display_errors', 1); error_reporting (E_ALL & ~E_NOTICE); // Connect and select. if ($dbc = @mysql_connect ('localhost', 'username', 'password')) { if (!@mysql_select_db ('myblog')) { die (' Could not select the database because: '. mysql_error(). ' ');}} else { die (' Could not connect to MySQL because: '. mysql_error(). ' ');} if (isset ($_POST['submit'])) { // Handle the form.
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Code Continued // Define the query. $query = "DELETE FROM blog_entries WHERE blog_id={$_POST['id']} LIMIT 1"; $r = mysql_query ($query); // Execute the query. // Report on the result. if (mysql_affected_rows() == 1) { print ' The blog entry has been deleted. ';} else { print " Could not delete the entry because: ". mysql_error(). ". The query was $query. ";}} else { // Display the entry in a form. // Check for a valid entry ID in the URL. if (is_numeric ($_GET['id']) ) { // Define the query. $query = "SELECT * FROM blog_entries WHERE blog_id={$_GET['id']}"; if ($r = mysql_query ($query)) { // Run the query. $row = mysql_fetch_array ($r); // Retrieve the information.
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Code Continued // Make the form. print ' Are you sure you want to delete this entry? '. $row['title']. ' '. $row['entry']. ' ';} else { // Couldn't get the information. print " Could not retrieve the entry because: ". mysql_error(). ". The query was $query. ";}} else { // No ID set. print ' You must have made a mistake in using this page. ';}} // End of main IF. mysql_close(); // Close the database connection. ?>
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Updating Data in a Database WHERE clause must be used or all the records in the database will be updated. If the values are strings they should be placed between single quotation marks.
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Updating Table Information <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Edit a Blog Entry <?php // Script 12.8 - edit_entry.php // This script edits a blog entry using an UPDATE query. // Address error handling. ini_set ('display_errors', 1); error_reporting (E_ALL & ~E_NOTICE); // Connect and select. if ($dbc = @mysql_connect ('localhost', 'username', 'password')) { if (!@mysql_select_db ('myblog')) { die (' Could not select the database because: '. mysql_error(). ' ');}} else { die (' Could not connect to MySQL because: '. mysql_error(). ' ');}
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Code Continued if (isset ($_POST['submit'])) { // Handle the form. // Define the query. $query = "UPDATE blog_entries SET title='{$_POST['title']}', entry='{$_POST['entry']}' WHERE blog_id={$_POST['id']}"; $r = mysql_query ($query); // Execute the query. // Report on the result. if (mysql_affected_rows() == 1) { print ' The blog entry has been updated. ';} else { print " Could not update the entry because: ". mysql_error(). ". The query was $query. ";}} else { // Display the entry in a form. // Check for a valid entry ID in the URL. if (is_numeric ($_GET['id']) ) { // Define the query. $query = "SELECT * FROM blog_entries WHERE blog_id={$_GET['id']}"; if ($r = mysql_query ($query)) { // Run the query. $row = mysql_fetch_array ($r); // Retrieve the information.
![Code Continued if (isset ($_POST[ submit ])) { // Handle the form.](http://images.slideplayer.com./12/3415692/slides/slide_21.jpg "// Define the query. $query = UPDATE blog_entries SET title= {$_POST[ title ]} , entry= {$_POST[ entry ]} WHERE blog_id={$_POST[ id ]} ; $r = mysql_query ($query); // Execute the query. // Report on the result. if (mysql_affected_rows() == 1) { print The blog entry has been updated. ;} else { print Could not update the entry because: . mysql_error(). . The query was $query. ;}} else { // Display the entry in a form. // Check for a valid entry ID in the URL. if (is_numeric ($_GET[ id ]) ) { // Define the query. $query = SELECT * FROM blog_entries WHERE blog_id={$_GET[ id ]} ; if ($r = mysql_query ($query)) { // Run the query. $row = mysql_fetch_array ($r); // Retrieve the information..")
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Code Continued // Make the form. print ' Entry Title: Entry Text: '. $row['entry']. ' ';} else { // Couldn't get the information. print " Could not retrieve the entry because: ". mysql_error(). ". The query was $query. ";} else { // No ID set. print ' You must have made a mistake in using this page. ';}} // End of main IF. mysql_close(); // Close the database connection. ?>
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How to Create Users and Privileges in MySQL Open the MySQL monitor and type the following: mysql> GRANT privileges ON database.* TO username IDENTIFIED BY ‘password’; Example: mysql> GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, ALTER ON companydb.* TO areej IDENTIFIED BY ‘aa7097’;
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