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C20.0046: Database Management Systems Lecture #20

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

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C20.0046: Database Management Systems Lecture #20

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

  4. Goals: after this week • Understand dynamic webpages • CGI • 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 • In Perl • In PHP • that • That do look-ups with user-entered parameters • And display the results • Based on examples from class 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 M.P. Johnson, DBMS, Stern/NYU, Spring 2005

  6. Dynamic webpages • Soln 1: upon url request • somehow decide to dynamically generate an html page (from scratch) • send back new html page to user • No html file exists on server, just created on demand • CGI/Perl, Java servlets, etc. 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: • user chooses an url •  webserver runs that url’s program, • sends back the program’s output M.P. Johnson, DBMS, Stern/NYU, Spring 2005

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

  9. Using CGI • CGI works with any prog./scripting lang. • Really? • Well, no, not really… 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 ifnobody has permission to use them • and if the necessary DB software is installed • Plausible choices: Perl, Python, C, sh M.P. Johnson, DBMS, Stern/NYU, Spring 2005

  11. CGI admin • Most webservers: CGI program/script must either • End in .cgi and/or • 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 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 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 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://google.com http://pages.stern.nyu.edu/~mjohnson/dbms/perl/lookup.cgi 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 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.html 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"; sales% perl hello.pl Hello World sales% 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 • What’s wrong? • http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello.cgi • What’s wrong? • http://pages.stern.nyu.edu/~mjohnson/dbms/perl/hello2.cgi • What’s wrong? M.P. Johnson, DBMS, Stern/NYU, Spring 2005

  19. Troubleshooting hello.cgi • Get the extension right: • Try running with perl: • Are there Perl errors? • Try running as program: • Are the execute permissions on? sales% cp hello.pl hello.cgi sales% perl hello.cgi sales% ./hello.cgi sales% chmod +x hello.cgi 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"; 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"; 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(); 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/cgipm.pl • http://pages.stern.nyu.edu/~mjohnson/dbms/perl/cgipm.cgi • Somewhat simpler, but another thing to learn • Mostly won’t cover Review: Hello, World 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; 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”; 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” 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"; $s = 10; $s = 3.5; 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‘ print ("Hello ", "Dolly", ".\n"); $name = "Dolly"; print ("Hello $name.\n"); 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 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/ • Perl Basics: • http://www.cs.wcupa.edu/~rkline/Perl/perl-basics-1.html • CGI Basics: • 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 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/ • Interactive PHP with database access: • 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 • Nice insert/update/delete example from webmonkey: • 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 M.P. Johnson, DBMS, Stern/NYU, Spring 2005

  32. For next time… • Go through at least one tutorial each on Perl and PHP • Try posting a hello-web Perl script in your sales account • 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 M.P. Johnson, DBMS, Stern/NYU, Spring 2005

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