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CSCI 297 Scripting Languages
Misc Odds and Ends CSCI 297 Scripting Languages
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Today Database Normalization Data Backups
Tracking the User with Cookies Short example of SQL Injection
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Database Normalization
Goal = each piece of information exists only once in the database creates storage efficiency more efficient to update duplicates can create inaccuracies First Normal Form no repeating columns with same data types all columns contain single value primary key uniquely identifies each row Second Normal Form rows do not duplicate information Third Normal Form data not dependent on the primary key is moved to another table
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Normalization Example
First Order no primary key First Order two columns w/ same data type Second Order two rows with same info Author1 Author2 Title ISBN Price CustName CustAddr MW Brown C. Hurd Good Night Moon 1234 12.99 Claire Dannelly 980 Eagle, Rock Hill… D. Pilkey Captain Underpants 6789 24.50 William Dannelly Bob Smith 123 Main… ISBN Author 1234 Marguerite Wise Brown Clement Hurd 6789 Dav Pilkey ISBN Title Price 1234 Good Night Moon 12.99 6789 Captain Underpants 24.50
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Backing Up Data Full Database Back Up Full Database Restore
big pain two possible options from the command line: mysqldump --opt --all-database > all.sql mysqlhotcopy database /path/for/backup Full Database Restore it's a really long set of complicated steps If concerned about data corruption lock the table(s) copy the records to a copy of the table(s) unlock the table(s) Transactions - updates can be temporary
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Cookies - setting in PHP
setcookie (name, value, expire, path, domain); name name of the cookie value example: "usrname" value the value of the cookie example = "Bob Smith" expire time of when the cookie expires if empty, then the cookie expires when the browser closes example : 24 hours from now = time()+24*60*60
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Cookies - very simple example
Problem : Script to either display the user name that is stored in a cookie or save the user name into a cookie Possible Conditions while running the script: a cookie was already set isset ($_COOKIE[…]) the cookie is being set with form data isset ($_POST[…]) the cookie has not been set neither of the above is true
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<?php // we have been here before and the cookie is set if (isset($_COOKIE["usrname"])) echo "Welcome " . $_COOKIE["usrname"] . "<P>"; // script is setting the cookie, expires in two minutes else if (isset($_POST['usrname'])) { setcookie ("usrname", $_POST['usrname'], time()+120); echo "Setting the cookie<P>"; } // first time visitor else echo "Welcome first time visitor<P>"; echo "<form action='cooktest1.php' method='Post'>"; echo "User Name: <input type='text' name='usrname'><br>"; echo "<input type=submit value='Save Name'<P>"; echo "</form>"; ?>
![< php // we have been here before and the cookie is set if (isset($_COOKIE[ usrname ])) echo Welcome .](http://slideplayer.com/slide/17919018/108/images/8/%3C+php+%2F%2F+we+have+been+here+before+and+the+cookie+is+set+if+%28isset%28%24_COOKIE%5B+usrname+%5D%29%29+echo+Welcome+..jpg "$_COOKIE[ usrname ] . <P> ; // script is setting the cookie, expires in two minutes else if (isset($_POST[ usrname ])) { setcookie ( usrname , $_POST[ usrname ], time()+120); echo Setting the cookie<P> ; } // first time visitor else echo Welcome first time visitor<P> ; echo <form action= cooktest1.php method= Post > ; echo User Name: <input type= text name= usrname ><br> ; echo <input type=submit value= Save Name <P> ; echo </form> ; > .")
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Cookies - common error The setcookie() function must appear before the <html> tag. This code is okay: else if (isset($_POST['usrname'])) { setcookie ("usrname", $_POST['usrname'], ... echo "The cookie is set.<P>"; } This code generates an error: echo "Setting the cookie...<P>";
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SQL Injection Example $username = $_POST['username']; $password = $_POST['password']; $query = "SELECT 'id' FROM 'users' WHERE 'username' = '$username' AND 'password' = '$password';" $result = mysqli_query ($DBconn, $query); if (mysqli_num_rows($result) == 0) error : try again else user is okay
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example continued… PHP String with SQL Command:
SELECT 'id' FROM 'users' WHERE 'username' = '$username' AND 'password' = '$password'; What if the user enters: username ==> ' OR ''=' password ==> ' OR ''=' The resulting SQL Command: 'username' = '' OR ''='' AND 'password' = '' OR ''='';
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