Re: Quickest way of fetching a Single row and column in MySQL using DBI

[Anonymous Monk]

Nvm...found it.

for future ref.

my $id = $dbh->selectrow_arrayref("SELECT id FROM users where username
+ = '$username'");

[cees]

Although your version works, it is potentially open to an SQL injection attack through the $username variable. With DBI that is easy to avoid by using placeholders. Also, I think you want selectrow_array (selectrow_arrayref returns a reference to an array, wheras selectrow_array will return a list, or just a scalar value if you are selecting a single column).

my $id = $dbh->selectrow_array("SELECT id FROM users where username = 
+?", {}, $username);

[perrin]

I think you need array context there:

my ($id) = $dbh->selectrow_array("SELECT id FROM users where username 
+= ?", {}, $username);

[cees]

Scalar context works as well according to the DBI source code:

sub selectrow_array {
  my $row = _do_selectrow('fetchrow_arrayref', @_) or return;
  return $row->[0] unless wantarray;
  return @$row;
}

The docs hint that this should work as well, but don't explicitly state it. Instead the docs mention this:

If called in a scalar context for a statement handle that has more than one column, it is undefined whether the driver will return the value of the first column or the last. So don't do that.

Anyway, it won't hurt to add the brackets in there to force list context, but it shouldn't be required.