GUFE Walkthrough: Part 3

sub openDB {
#open connection to database
my ($DBD,$dbase,$dbuser,$dbpassword)=@_;
my $dbh = DBI->connect("dbi:$DBD:$dbase",$dbuser,$dbpassword)
               || die "could not connect to database!";
return $dbh;
} #end openDB

Establishing the connection to the database is fairly simple, and that's just what the &openDB subroutine does. Four parameters are sent to this subroutine when it is called -- the DBD protocol to use (such as "mysql" or "ODBC"), the database to connect to (such as "Clients"), and if necessary a username and password. Some databases, such as those in MySQL, can be protected requiring login. You can see that parameters passed to a subroutine wind up in the Perl built-in variable @_, a list of each value sent in.

If for some reason the connection should fail, the subroutine "dies", meaning that it exits to the browser with an error message.

sub sendSQL {
#send SQL query
my ($sqlstatement,$dbh)=@_;
my $sth = $dbh->prepare($sqlstatement);
$sth->execute ||
       die("Could not execute SQL statement ... maybe invalid?".
           "<br>Here is the statement that choked: $sqlstatement");
return $sth;
}#end sendSQL

The &sendSQL subroutine, while extremely important to GUFE, is also quite simple. That's because interpreting and processing SQL statements is the job of the database itself. In short, &sendSQL receives the SQL statement and the database handle. Then, using standard DBI syntax, it prepares and executes the SQL statement at the database engine. The final result of this is a statement handle, which is returned from the subroutine, and which we later use to access the actual data returned by the database in response to the query. It is with this statement handle, $sth, that we'll do much of our work.

GUFE Walkthrough: Part 2
The Perl You Need to Know
GUFE Walkthrough: Part 4