为什么mysql在似乎没有时会给我一个语法错误？

Question

The following code is runnable and works fine but if I change $dbh->do("set names utf8"); to $dbh->do("set names gbk"); , I will receive a syntax error:

use strict;
use warnings;
use DBD::mysql;

my $dbh = DBI->connect("DBI:mysql:database=test;host=localhost","root","password");
$dbh->do("set names utf8");

open  my $jpg, '<', 'test.jpg' or die "$!";
binmode $jpg;
my $image = do{local $/; <$jpg>};
close $jpg;

 my $sql = "INSERT INTO student VALUES (?, ?)";

 my $sth = $dbh->prepare($sql);
 $sth->bind_param(1, 'Yang Liu');
 $sth->bind_param(2, $image);   
 $sth->execute();
 $sth->finish;
 exit;

The syntax error reads as follows:

DBD::mysql::st execute failed: You have an error in your SQL syntax; check the m
anual that corresponds to your MySQL server version for the right syntax to use
near 'id=\'W5M0MpCehiHzreSzNTczkc9d\'?>\n<x:xmpmeta xmlns:x=\'adobe:ns:meta/\' x
:xmptk' at line 1 at D:\sqltest.pl line 22.
DBD::mysql::st execute failed: You have an error in your SQL syntax; check the m
anual that corresponds to your MySQL server version for the right syntax to use
near 'id=\'W5M0MpCehiHzreSzNTczkc9d\'?>\n<x:xmpmeta xmlns:x=\'adobe:ns:meta/\' x
:xmptk' at line 1 at D:\sqltest.pl line 22.

And the suspicious line that reads 'id=\\'W5M0MpCehiHzreSzNTczkc9d\\'?>\\n<x:xmpmeta xmlns:x=\\'adobe:ns:meta/\\' is associated with the test.jpg image file which I'm trying to store to the longblob as I can find the same string if I open the image file using a text editor.

It's weird that code also works if I change $dbh->do("set names utf8"); to $dbh->do("set names gb2312"); Why the set names gbk statement gives me a syntax error? Is there something obvious that I'm doing wrong?

Thanks in advance:)

I'm running ActivePerl 5.10.1 and MySQL 5.5.

UPDATE

I've found the culprit!

This line local $/; is causing a MySQL syntax error. To fix the problem, simply comment out this line.

My Perl script is encoded in GBK and my database table encoding is also GBK, but I have to also add the set names to gbk to the DBI in perl, otherwise, GBK characters inserted into the table won't display properly in a GBK environment.

UPDATE2

I thought I had fixed the problem but the problem is actually still there. When I delete the local $/; line, there's no error message but the blob field contains a corrupted image file.

Answer 1

GBK is outdated, you must not use it anymore; and MySQL does not support the current standard GB 18030.

• http://dev.mysql.com/doc/refman/5.5/en/faqs-cjk.html#qandaitem-B-11-1-1
• http://www.gb18030.com/
• http://zh.wikipedia.org/wiki/GB_18030

Work-around: do not set names , and deal with encoding of text in Perl only. Keep binary data such as images as octets.

use utf8;
use Encode qw(encode);
use Encode::HanExtra qw();
⋮
my $name = encode('GB18030', '刘阳', Encode::FB_CROAK | Encode::LEAVE_SRC);
$dbh->do(
    'INSERT INTO student VALUES (?, ?)',
    {},
    $name, $image
);

(I have not tested this code.)

Answer 2

com/users/183467/mike ,

I solved this by using the function addslashes($img). Without it the img var contain chars that need to be covered by a slash to allow them in database properly.. Otherwise, it seems such chars would blend with your sql code and get misread as syntax errors.

That's why even after you removed the appearance the error message the image was not stored the right way.