There are of course exceptions. If you have access to the machine the MySQL server runs on, you have the appropriate permissions, you know where the server keeps its datafiles, and you know the structure of said files (and directories), you can find out. You also might be able to find out whether the database exists by peeking in the appropriate log file.

Abigail

you can't determine whether you still have ice-cream without opening the freezer.

I beg to differ. What if you happen to have a freezer with a transparent door? I could very well see if there is ice cream without opening it. ;)

Only if you defrost the freezer daily. Otherwise, the inside will be frosted up, and you can't see through it. Since you post here, you are either a nerd or a geek, or both, and nerds and geeks don't defrost their freezers daily.

Besides, you never fixed the broken light in the freezer, and even after you fixed it, you don't know whether there's ice-cream hiding behind the frozen spinach.

Abigail

so what can i do about it now? this scripts fails to execute if the database doesnt exist!! so its not working properly! what can i do to fix it?

Uhh .. errr ... uhhh ... check for return values and do what you need to? Basically, you're doing a bunch of stuff without checking return values. Also, you have RaiseError set on one of your connects so you could wrap the code inside an eval.

my $dbh = DBI->connect( $dsn, $user, $password,
                                     { RaiseError => 1 } );

if( ! $dbh ) {
    print "Ugg, connection problem: $DBI::errstr\n";
} else {
     eval {
          $dbh->do( whatever );
          $dbh->do( something else );
    };
 
    if( $@ ) {
        print "Ugg, problem: $@\n";
    }
}
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-derby

Either of two things: check the return value of the connect method, and if it fails, check the reason. Or connect to a database you know exists, and once connected, check to see whether the database you are interested in exists.

Abigail

If it doesn't exist you'll get undef for $db. Check the return value of your connect and do something appropriate.

is this ok to use?

if ($db1) { $db=$db1 );
if ($db2) { $db=$db2 );
if (!$db1 and !$db2) { print font( {-size=>5, -color=>'Lime'}, "$DBI::
+errstr"; exit() );
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is this correct?

$db1 = DBI->connect("DBI:mysql:nikos_db", "root", "") or
$db2 = DBI->connect("DBI:mysql:nikos_db:50free.net", "nikos_db", "macg
+yver");

if (!$db2 and $db1) { print font( {-size=>5, -color=>'Lime'}, "$DBI::e
+rrstr" ); $db=$db1; }
if (!$db1 and $db2) { print font( {-size=>5, -color=>'Lime'}, "$DBI::e
+rrstr" ); $db=$db2; }

$db->do( "drop database if exists nikos_db" );
$db->do( "create database nikos_db" );
$db->do( "use nikos_db" );
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i want my script to be able to determine if it runs on localhost or if it runs on the remote server. and also if it fails to connct to the mysql server to give the appropriate message for localhost and appropriate message for the remote web server! id the above code correct? thank you!

You might want to use DBI->data_sources or _ListDBs to get a list of available databases for a mysql server. See Private MetaData Methods inside DBD::mysql for more information.

If what you are looking for is to find out if the database server is running, just try to do a DBI->connect and check to see if the returned object is defined, probably with RaiseError set to 0 if you think it isn't a fatal condition.

Regards,
techy

It seems what you're actually asking about is behaving in different ways based on different servers, rather than checking a database exists: you want one configuration on one server, and a different one on another.

What you could do is check the contents of $ENV{'SERVER_NAME'} , and attempt to connect based on the contents of that. Maybe (it's a bit simple):

my $db;
if ($ENV{'SERVER_NAME'} eq '50free.net') {
  $db = DBI->connect (...); # your public server
} else {
  $db = DBI->connect (...); # your home server
}
if (! defined $db) {
  # there was an error
}
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