1. M.P. Johnson, DBMS, Stern/NYU, Spring 20051 C20.0046: Database Management Systems Lecture #20 M.P. Johnson Stern School of Business, NYU Spring, 2005

2. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 2 Homework Project part 4 due Thursday  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  Assigned after Thursday  Due: end of semester

3. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 3 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

4. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 4 Goals: after this week Understand dynamic webpages 1. CGI 2. PHP-like scripting Today: be able to post a hello-web Perl program in your sales account This week: Be able to write simple dynamic webpages in 1. In Perl 2. In PHP that 1. That do look-ups with user-entered parameters 2. And display the results 3. Based on examples from class

5. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 5 New topic: web apps Goal: web front-end to database  Present dynamic content, on demand  Not canned (static) pages/not canned queries  (perhaps) modify DB on demand Naïve soln: static webpage & HTTP  index.html written, stored, put on server, displayed when it’s url is requested  HTTP is stateless (so?)  This doesn’t solve our problem

6. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 6 Dynamic webpages Soln 1: upon url request 1. somehow decide to dynamically generate an html page (from scratch) 2. send back new html page to user  No html file exists on server, just created on demand  CGI/Perl, Java servlets, etc.

7. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 7 New topic: CGI First, and still very popular method CGI: Common Gateway Interface  Not a programming language!  Just an interface (connection) between the webserver and an outside program “Webserver” = webserver software, e.g., Apache  Very simple basic idea: 1. user chooses an url 2.  webserver runs that url’s program, 3. sends back the program’s output

8. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 8 On-the-fly content with CGI Program Client Server HTTP Request Data for program Generated HTML HTML Image from http://www.scit.wlv.ac.uk/~jphb/cp3024/

9. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 9 Using CGI CGI works with any prog./scripting lang. Really? Well, no, not really…

10. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 10 CGI works… if the webserver machine can run program  pages/soho, not sales and if the user the webserver is running as (e.g. nobody) can can run your program and if the necessary jars/libraries are available and if nobody has permission to use them and if the necessary DB software is installed Plausible choices: Perl, Python, C, sh

11. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 11 CGI admin Most webservers: CGI program/script must either 1. End in.cgi and/or 2. Reside in cgi-bin Ours: needs.cgi extension If an actual program, the cgi file is just the name of the executable: gcc -o myprog.cgi myproc.gcc

12. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 12 CGI admin In a script, first (“shebang”) line says which interpreter to use: Either way, cgi file must be executable: Make sure your cgi file runs at cmd prompt:  But not a guarantee! #!/usr/local/bin/perl sales% chmod +x *.cgi sales%./myprog.cgi

13. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 13 CGI input CGI programs must respond to input Two mechanisms:  GET: read env. var. QUERY_STRING  POST: get length from env. var. CONTENT_LENGTH; read from STDIN This diff. mostly invis. to Perl, PHP Both send a sequence of name/value pairs, separated by &s: name=a&submit=Search

14. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 14 CGI input Appearance/security differences GET: string is part of the URL, following a ?: POST: string can be read by program from an environmental variable  Vars not visible to the browser user  Not automatically put in server log, etc. http://pages.stern.nyu.edu/~mjohnson/dbms/ perl/lookup.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/ perl/lookup.cgi http://google.com

15. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 15 Our use of CGI We’ll discuss CGI and Perl  One option for your project  Can try C, C++, etc.  But not recommended! For CGI, only Perl will be “supported”  Scripting languages v. programming languages  Development v. IT  Other languages are still not recommended especially if you don’t know Perl and PHP

16. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 16 New topic: Just Enough Perl Very popular, powerful scripting language Very good at “regular expressions”, text manipulation, but not very relevant to us Instead:  simple text/html production  Basic language constructs  MySQL connectivity Perl = Practical Extraction and Report Language = Pathologically Eclectic Rubbish Lister perl -pi -e 's/tcsh/sh/' $HOME/.login See http://perl.org.il/pipermail/perl/2003-February/001047.htmlhttp://perl.org.il/pipermail/perl/2003-February/001047.html

17. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 17 hello.pl Hello, World - hello.pl Running at command prompt: #!/usr/bin/perl -w print "Hello World\n"; #!/usr/bin/perl -w print "Hello World\n"; sales% perl hello.pl Hello World sales% sales% perl hello.pl Hello World sales%

18. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 18 Hello, World - hello.pl Run from browser:  http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello.pl http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello.pl What’s wrong?  http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello.cgi What’s wrong?  http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello2.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello2.cgi What’s wrong?

19. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 19 Troubleshooting hello.cgi 1. Get the extension right: 2. Try running with perl:  Are there Perl errors? 3. Try running as program:  Are the execute permissions on? sales% perl hello.cgi sales%./hello.cgi sales% chmod +x hello.cgi sales%./hello.cgi sales% chmod +x hello.cgi sales% cp hello.pl hello.cgi

20. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 20 Troubleshooting hello.cgi 5. Make sure you’re printing the HTML header #! /usr/bin/perl -w print "Content-type: text/html\n\n"; print "Hello World\n"; #! /usr/bin/perl -w print "Content-type: text/html\n\n"; print "Hello World\n";

21. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 21 Troubleshooting hello.cgi 5.Show errors and warnings: http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello3.cgi  Is case-sensitive #! /usr/bin/perl -w use CGI qw(:standard); use CGI::Carp qw( fatalsToBrowser warningsToBrowser ); print header(); pr int "Hello World\n"; #! /usr/bin/perl -w use CGI qw(:standard); use CGI::Carp qw( fatalsToBrowser warningsToBrowser ); print header(); pr int "Hello World\n";

22. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 22 Perl and HTML headers Data sent to a browser is prefaced with a header describe type of data: Hand-generated html must print this before anything else: Or:  When use-ing CGI Content-type: text/html\n\n print "Content-type: text/html\n\n"; print CGI::header();

23. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 23 Perl, HTML, and CGI.pm CGI.pm offers a “front-end” to HTML  Replaces mark-up language with an API Very simple example:  http://pages.stern.nyu.edu/~mjohnson/dbms/perl/c gipm.pl http://pages.stern.nyu.edu/~mjohnson/dbms/perl/c gipm.pl  http://pages.stern.nyu.edu/~mjohnson/dbms/perl/c gipm.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/perl/c gipm.cgi Somewhat simpler, but another thing to learn Mostly won’t cover Review: Hello, World

24. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 24 More on Perl Perl is mostly “C-like” Perl is case-sensitive Use # for rest-of-line comments Creation of functions is supported but optional  Like PL/SQL Perl has “modules”/“packages” CGI module:  Provides header() function, easy access to CGI params Mysql module: use CGI qw(:standard); use Mysql;

25. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 25 Perl and strings Can use “ ” for strings Concatenate with. op: Print text with print function: Or, parentheses can be dropped! “Hi ”. “there\n” print (“Hi there”); print “Hi there”;

26. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 26 Perl and strings Can compare numbers (as numbers) with usual operators  <=, etc.  3 < 5 These do not apply to strings String ops are based on initials of operations:  eq, ne, lt, gt, le, ge  “hi” ne “there”  “hi” le “hi there”

27. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 27 Perl and variables All regular variables begin with $  $input, $query Declare vars with my: Q: What about var types? A: Perl is loosely typed! my $s = "hi"; my $query = "select …"; my $s = "hi"; my $query = "select …"; my $s = "hi"; $s = 10; $s = 3.5; my $s = "hi"; $s = 10; $s = 3.5;

28. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 28 Perl, strings, and variables print takes var-many arguments: Variables are always “escaped” Vars may appear within strings: Prints out: Hello Dolly.  To prevent escaping, use single quotes '$name‘ $name = "Dolly"; print ("Hello $name.\n"); print ("Hello ", "Dolly", ".\n");

29. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 29 Perl syntax examples Access member/field of object ::  object::member Access member pointed to by object ->  rowhash->field Can access array members with indices Can access hash members with strings http://pages.stern.nyu.edu/~mjohnson/dbms/perl/controls.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/perl/controlscgi.txt

30. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 30 Tutorials on Perl Some material drawn from the following good tutorials: http://perl.com CGI backend programming using perl:  http://www.scit.wlv.ac.uk/~jphb/sst/perl/ http://www.scit.wlv.ac.uk/~jphb/sst/perl/ Perl Basics:  http://www.cs.wcupa.edu/~rkline/Perl/perl-basics-1.html http://www.cs.wcupa.edu/~rkline/Perl/perl-basics-1.html CGI Basics:  http://www.cs.wcupa.edu/~rkline/Perl/cgi-basics-1.html http://www.cs.wcupa.edu/~rkline/Perl/cgi-basics-1.html MySQL/Perl/CGI example:  http://www.scit.wlv.ac.uk/~jphb/sst/perl/ex3d.html http://www.scit.wlv.ac.uk/~jphb/sst/perl/ex3d.html

31. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 31 Tutorials on PHP Some material drawn from the following good tutorials: http://php.net PHP introduction and examples:  http://www.scit.wlv.ac.uk/~jphb/sst/php/ http://www.scit.wlv.ac.uk/~jphb/sst/php/ Interactive PHP with database access:  http://www.scit.wlv.ac.uk/~jphb/sst/php/gazdb.html http://www.scit.wlv.ac.uk/~jphb/sst/php/gazdb.html Longer PHP/MySQL Tutorial from webmonkey:  http://hotwired.lycos.com/webmonkey/99/21/index2a.html http://hotwired.lycos.com/webmonkey/99/21/index2a.html Nice insert/update/delete example from webmonkey:  http://hotwired.lycos.com/webmonkey/99/21/index3a.html http://hotwired.lycos.com/webmonkey/99/21/index3a.html MySQL/Perl/PHP page from U-Wash:  http://www.washington.edu/computing/web/publishing/mysql-script.html http://www.washington.edu/computing/web/publishing/mysql-script.html

32. M.P. Johnson, DBMS, Stern/NYU, Spring 2005 32 For next time… 1. Go through at least one tutorial each on Perl and PHP 2. Try posting a hello-web Perl script in your sales account 3. Run/read these: http://pages.stern.nyu.edu/~mjohnson/dbms/perl/controls.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/perl/controlscgi.txt http://pages.stern.nyu.edu/~mjohnson/dbms/perl/lookup.cgi http://pages.stern.nyu.edu/~mjohnson/dbms/perl/lookupcgi.txt