Perl - 在没有主键的情况下更新 mysql 表

Question

I have a table with no primary key. I need to execute the following:

UPDATE t1
   SET tstamp = now()
 WHERE `col1` = 1
   AND `col2` = 'this';

In Workbench it throws Error 1175 until I execute this line before the update:

SET SQL_SAFE_UPDATES = 0;

With this line it works just fine.

But when I try to do this in perl it doesn't work. I tried both

$dbh->do("SET SQL_SAFE_UPDATES = 0");

and

my $dbh = DBI->connect("DBI:mysql:$db:$host:$port",$user,$password, { RaiseError => 1, AutoCommit => 0, sql_safe_updates => 0 })

but it still doesn't work.

How can I get this work in perl?

UPD. I updated the code with @@sql_safe_updates check and commit.

The code:

$sth = $dbh->prepare("SELECT @\@sql_safe_updates"); $sth->execute; while(my @row = $sth->fetchrow_array) { print "sql_safe_updates before: ". $row[0] . "\n"; }

$dbh->do("SET SQL_SAFE_UPDATES = 0") or die $dbh->errstr;

$sth = $dbh->prepare("SELECT @\@sql_safe_updates"); $sth->execute; while(my @row = $sth->fetchrow_array) { print "sql_safe_updates after: " . $row[0] . "\n"; }

$query = "UPDATE t1 SET tstamp = now() WHERE `col1` = 1 AND `col2` = 'this'";
$sth = $dbh->prepare($query);
$rv = $sth->execute or die $sth->err();
$dbh->commit;
if ("$rv" ne "1") {
    $query =~ s/\n/ /g; $query =~ s/  / /g;
    print "Failed to run query: $query\n";
   exit;
}

Output:

sql_safe_updates before: 0
sql_safe_updates after: 0
Failed to run query: UPDATE t1 SET tstamp = now() WHERE `col1` = 1 AND `col2` = 'this'

UPD2. I checked the table - everything works after I commited. It is confusing thought, that $rv is 1 on successful select and 2 on successful update

Answer 1

It was a return code check error, and a missing commit.

Regarding the return code check, for a non- SELECT statement, execute returns the number of rows affected, if known. . Zero rows affected (as opposed to an error) is represented as the special "zero but true" value "0E0". In the OP's case, the statement was returning 2.