adhi .b adhi .b - 1 year ago 67
Perl Question

Why am I getting 0E0 for the return value of the DBI "execute" method?

I have written a sample Perl program to delete data from a database table.

This is the code I have written,

use DBI;

my $dbh = DBI->connect("DBI:Pg:host=;port=5432;", "adhi");
if ( $dbh ) {

print "Connected successfully\n";

my $exe = $dbh->prepare("delete from perl_test.test");
my $res = $exe->execute();
if ( $res ) {
print "deleted the table successfully of rows: $res\n";

If I have executed the above it should print successful message and then the number of rows deleted.

If the table was empty it was printing
instead of
I don't know how it is returning the value like this?

Can someone please explain me how it was working?

Answer Source

It is done in this way to allow to test whether the operation was successful. The reason is that '0E0' (as a string) is a true value, but 0 is a false value in Perl. Therefore:

  1. you can test the return value in if to determine whether the operation was successful (true means success),

  2. but you can also use the return value as a number to know the exact number of deleted rows, since 0E0 evaluates to 0 when used as a number.

If you need just the number of deleted rows, you can use $res + 0 or $res * 1. But only after you have tested that the operation was successful.

More about true and false values: True and false

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