SQL Insert/Update does fails, does not invoke errors - mysql

Question

Afternoon everyone,
I'm currently trying to insert or update form field values via params into a mysql after some simple validation. The form submits, but does not actually execute any of the operations and does not raise a syntax or database connection error. I know my connection string works because I fetched values from it to compare to in the code prior to the nested evaluation blocks shown below. The foreach loops were inserted as an alternate means of validating that the values have indeed been altered in the table. Your help is greatly appreciated, as always:
my $dbusr = param("dbuser");
my $dbpw = param("dbpass");
my $dbmail = param("dbemail");
my $dbtel = param("dbphone");
my $postflag = param("Submit");
if ($dbusr ne "") {
$sth = $dbh->prepare("SELECT * FROM USER WHERE username LIKE ?");
$sth->execute('$dbusr');
warn( $DBI::errstr ) if ( $DBI::err );
my #results = $sth->fetchall_arrayref();
foreach(#results){
if ($dbusr eq $_){
$loopval = 1;
}
}
unless($loopval){
$sth = $dbh->prepare("INSERT INTO USER
(username, password, phone, email)
values
(?,?,?,?)");
$sth->execute($dbusr, $dbpw, $dbtel, $dbmail);
warn( $DBI::errstr ) if ( $DBI::err );
$sth = $dbh->prepare("SELECT * FROM USER WHERE username LIKE ?");
$sth->execute('$dbusr');
#results = $sth->fetchall_arrayref();
foreach(#results){
if ($dbusr eq $_){
$successflag = 1;
}
}
}
else{
$sth = $dbh->prepare("UPDATE USER
SET (password = ?, phone = ?, email = ?)
WHERE username = ?");
$sth->execute($dbpw, $dbtel, $dbmail, $dbusr);
warn( $DBI::errstr ) if ( $DBI::err );
$sth = $dbh->prepare("SELECT * FROM USER WHERE username LIKE ?");
$sth->execute('$dbusr');
#results = $sth->fetchall_arrayref();
foreach(#results){
if ($dbusr eq $_){
$successflag = 1;
}
}
}
}

Answer 1

Basic Perl: '-quoted strings do NOT interpolate variables:
$sth->execute('$dbusr');
^-- ^---
You're literally passing $, d, b, etc... to your query as the placeholder value.
Try
$sth->execute($dbusr); // note the lack of ' quotes
instead.

Answer 2

You are searching for entire rows with the SELECT * FROM USER WHERE username LIKE ? statement, and are then fetching all the rows in one go with
my #results = $sth->fetchall_arrayref();
That method "returns a reference to an array that contains one reference per row.", but you are treating the returned value as an list of usernames:
foreach(#results){
if ($dbusr eq $_){
$loopval = 1;
}
}
To make this work you should just fetch the username column, and treat the returned rows as references of references. And as you look for exact matches in the database replace LIKE with =:
$sth = $dbh->prepare("SELECT username FROM USER WHERE username = ?");
$sth->execute($dbusr); # no quoting
die( $DBI::errstr ) if ( $DBI::err ); # what else to do if the execute fails?
my $results = $sth->fetchall_arrayref(); # an arrayref is returned
foreach(#$results){ # de-reference the array
if ($dbusr eq $_->[0]){ # each row is an arrayref, look in first element
$loopval = 1;
}
}
(Of course the same applies to the second search.)