how to validate username with DataBase in PerlCGI

[jaigs_27]

I want to do following in PerCGI:-

i) Want to validate "username" is already exists in DataBase or not?
ii) Can I check whether $sth contains some values or not from below mentioned statement?
iii) If $sth is not containing any value, means $user is not exists in Database then what'll fetchrow_array return.

$sql = Select * from userinfo where username=$user;
my $sth = $dbh->prepare($sql);
$sth->execute;
my @row = $sth->fetchrow_array

Please help me

Thanks

[Cabhan]

First off, remember to quote your assignment to $sql.

Secondly, so you want to know the number of rows that some query returns. This can be done by changing your SQL query and doing the following:

my $sql = "SELECT COUNT(*) FROM userinfo WHERE username = ?";
my $sth = $dbh->prepare($sql);
$sth->execute($user);
my $count = $sth->rows;

$count now contains the number of rows that have a username of $user.

Alternatively, as per the CPAN documentation of the DBI module:

If there are no more rows or if an error occurs, then fetchrow_array returns an empty list.

You might prefer fetchrow_arrayref, because:

If there are no more rows or if an error occurs, then fetchrow_arrayref returns an undef.

And an undef is simple to check for.