How do I bind DBI parameters at runtime in Perl? - perl

Question

I have the following code :
sub run_query {
my $name = shift || undef;
my $sql = (defined $name ) ? "select * from table where name = ?" :
"select * from table";
my $sth = $dbh->prepare("$sql");
$sth->execute($name);
}
The above subroutine need to work as follows: if $name is provided, then run the first query, else fetch all the data from the table. How can I bind the name field? I'd like it bound dynamically if it is provided.

Answer 1

From the DBI documentation on cpan:
A common issue is to have a code fragment handle a value that could be
either defined or undef (non-NULL or NULL) at runtime. A simple
technique is to prepare the appropriate statement as needed, and
substitute the placeholder for non-NULL cases:
$sql_clause = defined $age ? "age = ?" : "age IS NULL";
$sth = $dbh->prepare(qq{
SELECT fullname FROM people WHERE $sql_clause
});
$sth->execute(defined $age ? $age : ());
It does not exactly apply to your question, which I assume is that your execute fails if you add an argument where one is not expected. So, the last line here would apply:
$sth->execute(defined $name ? $name : ());

Answer 2

You should probably have two different subs, but you could use
sub run_query {
my $sql = #_
? "select * from table where name = ?"
: "select * from table";
my $sth = $dbh->prepare($sql);
$sth->execute(#_);
}

Answer 3

You can conditionally omit parameters if $name is not defined:
$sth->execute(defined $name ? $name : ());