我不明白undef
这段代码在做什么:
$dbh->do (qq {
INSERT INTO todo SET t = NOW(), status = 'open', content = ?
}, undef, $content);
有人可以解释一下吗?我想我理解了整个代码,但不是我理解的。
use warnings;
use strict;
use lib q(/data/TEST/perl/lib);
use CGI qw(:standard);
use WebDB;
sub insert_item {
my $content = shift;
my $dbh;
$content =~ s/^\s+//;
$content =~ s/^\s+$//;
if ($content ne "") {
$dbh = WebDB::connect();
$dbh->do (qq {
INSERT INTO todo SET t = NOW(), status = 'open', content = ?
}, undef, $content);
$dbh->disconnect();
}
}
sub display_entry_form {
print start_form(-action=> url()),
"To-do item:", br (),
textarea ( -name => "content",
-value => "",
-override => 1,
-rows =>3,
-columns => 80),
br (),
submit(-name=> "choice", -value => "Submit"),
end_form();
}
print header(), start_html(-title=>"To-Do List", -bgcolor => "white"), h2("To-Do List");
my $choice = lc(param ("choice"));
if ($choice eq "") {
display_entry_form();
} elsif ( $choice eq "submit" ) {
insert_item(param("content"));
display_entry_form();
} else {
print p ("Logic error, unknown choice: $choice");
}
该do()
方法采用3个参数:查询,查询属性和绑定数据。在undef
你的榜样手段,有没有属性适用。
$rows = $dbh->do($statement) or die $dbh->errstr;
$rows = $dbh->do($statement, \%attr) or die $dbh->errstr;
$rows = $dbh->do($statement, \%attr, @bind_values) or die ...
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