Question

I’m writing a subroutine for DBI updates, and are having some trouble figuring out how to add placeholder and stuff…

I have this:

sub row_update {   my $table = shift;   my %updates = @_;   my $placeholders = ...    $dbh->do('UPDATE $table SET (foo) WHERE (bar)') etc... } 

Any ideas?

I just want a simple update function where I can send in x number of arguments (as a hash).

Thanks in advance!

Answer 1

If I understand the question correctly, it sounds like you’re after SQL::Abstract. First, we create an SQL::Abstract object:

use SQL::Abstract; my $sql = SQL::Abstract->new; 

Now, as an example, we’ll use it to insert some data into a table:

my %record = (     FirstName  => 'Buffy',     LastName   => 'Summers',     Address    => '1630 Revello Drive',     City       => 'Sunnydale',     State      => 'California',     Occupation => 'Student',     Health     => 'Alive', );  my ($stmt, @bind) = $sql->insert(’staff’,\%record); 

This results in:

$stmt = 'INSERT INTO staff                 (FirstName, LastName, Address, City,                  State, Occupation, Health)                  VALUES (?, ?, ?, ?, ?, ?, ?)';  @bind = ('Buffy','Summers','1630 Revello Drive',          'Sunnydale',’California','Student','Alive'); 

The nice thing about this is we can pass it directly to DBI:

 $dbh->do($stmt, undef, @bind); 

Of course, you want to be updating records, not just inserting them. Luckily, this is also quite easy:

my $table = 'People';  my %new_fields = (     Occupation => 'Slayer',     Health     => 'Dead', );  my %where = (     FirstName => 'Buffy',     LastName  => 'Summers', );  my ($stmt, @bind) = $sql->update($table, \%new_fields, \%where);  $dbh->do($stmt, undef, @bind); 

This produces:

$stmt = 'UPDATE People SET Health = ?, Occupation = ?           WHERE ( FirstName = ? AND LastName = ? )';  @bind = ('Dead', 'Slayer', 'Buffy', 'Summers'); 

If you’re after more information about SQL::Abstract, I recommend you look at its CPAN page. There’s also a chapter in Perl Training Australia‘s Database Programming with Perl manual, which are freely available from our course notes page.

All the best,

Paul

Disclaimer: I’m managing director of Perl Training Australia, and therefore think that our course notes are pretty good.