M.P. Johnson, DBMS, Stern/NYU, Spring C : Database Management Systems Lecture #21 M.P. Johnson Stern School of Business, NYU Spring, 2005

M.P. Johnson, DBMS, Stern/NYU, Spring Homework Project part 4 due today  Topic: populating your tables with data  Using MySQL’s bulk loader  Start early!  Turn in on time Project part 5  Topic: web interface + any remaining loose ends  Posted soon…  Due: end of semester

M.P. Johnson, DBMS, Stern/NYU, Spring Agenda: Programming for SQL Have now been exposed to:  Embedded SQL: Pro*C  Java JDBC  Stored Procedures: PL/SQL All used; good to know about Most important for this course:  DB-conn from web scripting languages  DBI/DBDs in Perl, PHP

M.P. Johnson, DBMS, Stern/NYU, Spring Goals: after this week After Tuesday: be able to post a hello-web Perl script in your sales account After Today: 1. be able to post a hello-web PHP script in your sales account 2. Be able to modify/extend non-trivial Perl/PHP scripts to work with your DB Take input from user Execute SQL query Display formatted results

M.P. Johnson, DBMS, Stern/NYU, Spring Review: CGI/Perl Program Client Server HTTP Request Data for program Generated HTML HTML Image from

M.P. Johnson, DBMS, Stern/NYU, Spring New topic: HTML forms Interactive parts of HTML: forms Intuition for name: paper form  Fill in textboxes, check boxes or not, etc.  Turn it in (press button) HTML form  contains arb. # of INPUTs  Submits to somewhere (ACTION)  By GET or POST

M.P. Johnson, DBMS, Stern/NYU, Spring Form example On clicking Send, we go to the same page, but with “name=99&sumbit=OK” Enter a number: Enter a number:

M.P. Johnson, DBMS, Stern/NYU, Spring Perl and forms Obtain param number: Goal: display text and button;  On submit, tell user what was entered Improve: also print, say, triple the input… my $cgi = CGI->new(); $param = $cgi->param('number'); my $cgi = CGI->new(); $param = $cgi->param('number');

M.P. Johnson, DBMS, Stern/NYU, Spring Perl error-handling Many Perl scripts have lines of the form  some-statement OR die(“something happened”); What this means:  die exits with error message  Perl supports both || and OR as or operator  Perl supports boolean “short-circuiting” Boolean eval stops as fast as possible  Ftns often return 0/null/false for errors  if some-statement fails then we die

M.P. Johnson, DBMS, Stern/NYU, Spring Perl and databases DB connectivity is done through DBI  Database Interface  Analogous to Java’s JDBC  The steps correspond roughly 1-1 Think of DBI as a Java class with static methods Use these to obtain a connection, prepare and execute queries, etc.

M.P. Johnson, DBMS, Stern/NYU, Spring Perl DBI 1. Open a connection: 2. Prepare and execute query: my $dbh = DBI-> connect("dbi:mysql:database=mydb; mysql2.stern.nyu.edu;port=3306", user, pass); my $sth = $dbh->prepare($query); $sth->execute; my $sth = $dbh->prepare($query); $sth->execute;

M.P. Johnson, DBMS, Stern/NYU, Spring Perl DBI 3. Extract next row of data from statement results, if available:  What this means: row has two fields, whose values are put in $a and $b, in order  Other options, but this should suffice In general, want to scroll through results:  Braces { } are required! my ($a, $b) = $sth->fetchrow_array() while (my ($a, $b) = $sth->fetchrow_array()) { # print out $a and $b } while (my ($a, $b) = $sth->fetchrow_array()) { # print out $a and $b }

M.P. Johnson, DBMS, Stern/NYU, Spring Limit: Perl webpages that do something Semi-interesting Perl script:   Non-trivial but not huge: ~40 lines Works with two-column (a,b) table  Takes input from user  Returns rows whose a field contains value  If no/empty input, returns all rows Bad idea in general!

M.P. Johnson, DBMS, Stern/NYU, Spring lookup.cgi Two possible situations for running script: 1. Page opened for the first time 2. User entered parameter and pressed button Structure of file: 1. Print input box and button for next search  On button click, parameter is sent to this page’s url 2. (Try to) read input parameter 3. Open MySQL connection 4. Run query 5. Print results in a table 6. Disconnect from MySQL

M.P. Johnson, DBMS, Stern/NYU, Spring Higher-level structure As one page:  If we have params, display data based on them  Otherwise, prompt user for params, call self Could be:  Page 1: prompt for params, call page 2  Page 2: display data based on params In e.g.: always display data for convenience

M.P. Johnson, DBMS, Stern/NYU, Spring Tutorials on Perl Some material drawn from the following good tutorials: CGI backend programming using perl:  Perl Basics:  CGI Basics:  MySQL/Perl/CGI example: 

M.P. Johnson, DBMS, Stern/NYU, Spring That’s all, folks! Q: Is this enough to get a job coding Perl? A: Probably not! But: Don’t like Perl/CGI? Don’t want to run start a new process for every user/pageview/roundtrip of your site? Next we’ll do PHP… a couple modified copies of lookup.cgi and/or cia.cgi + some HTML glue  fairly interesting site a couple modified copies of lookup.cgi and/or cia.cgi + some HTML glue  fairly interesting site

M.P. Johnson, DBMS, Stern/NYU, Spring Dynamic webpages Original prob: need webpages to respond to user inputs Soln 2:  create a an html file embedded with special non- html code  upon url request, execute embedded code to generate more html/fill in the file  Send back the modified html page to user  An incomplete html page exists on server  Examples: PHP, JSPs, ASPs, etc.

M.P. Johnson, DBMS, Stern/NYU, Spring Review: dynamic webpages First option: for each request: run program, produce whole page, send back  CGI & some host language, Java Servlets, etc. Second option: create html page with missing parts; for each response, fill in the wholes and send back  Embedded scripting  PHP and others  PHP = Personal Home Page or = PHP Hypertext Processor

M.P. Johnson, DBMS, Stern/NYU, Spring hello.php Q: What the difference between and \n? Hello from PHP Here is the PHP part: \n“; ?> That's it! Hello from PHP Here is the PHP part: \n“; ?> That's it!

M.P. Johnson, DBMS, Stern/NYU, Spring hello2.php Script errors, w/ and w/o display_errors on:   Local dir must contain.htaccess:  Automatically load GET/POST params as vars  php_flag display_errors on php_flag register_globals on php_flag display_errors on php_flag register_globals on

M.P. Johnson, DBMS, Stern/NYU, Spring For next time… 1. Run/read these Perl scripts:

M.P. Johnson, DBMS, Stern/NYU, Spring For next time… 2.Run/read these PHP scripts: Various others in dbms/perl and dbms/php…dbms/perldbms/php