Re: Re: What is truth? (Curiosity corner)

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in thread What is truth? (Curiosity corner)

Yeah, it does indeed. I'm not quite sure why "0 but true" is often preferred. Maybe because it's more explicit about its intention?

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Re: Re: Re: What is truth? (Curiosity corner) by htoug (Deacon) on Jan 08, 2002 at 15:54 UTC
"0E0" is used by the DBI (and DBD's) for eg. `$sth->execute` when the SQL-statement processed 0 rows but did not error. This allows constructions like `my $rows=$sth->execute or die "SQL error"` ( Of course this would be expressed better using `$dbh->{RaiseError} = 1`). The relevant part of the DBI documentation states: For a non-`SELECT' statement, `execute' returns the number of rows affected, if known. If no rows were affected, then `execute' returns "`0E0'", which Perl will treat as 0 but will regard as true. Note that it is not an error for no rows to be affected by a statement. If the number of rows affected is not known, then `execute' returns -1.	[reply] [d/l] [select]

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Re: Re: Re: What is truth? (Curiosity corner)
by htoug (Deacon) on Jan 08, 2002 at 15:54 UTC

$sth->execute

This allows constructions like my $rows=$sth->execute or die "SQL error" ( Of course this would be expressed better using $dbh->{RaiseError} = 1).

The relevant part of the DBI documentation states:

For a non-`SELECT' statement, `execute' returns the number of rows affected, if known. If no rows were affected, then `execute' returns "`0E0'", which Perl will treat as 0 but will regard as true. Note that it is not an error for no rows to be affected by a statement. If the number of rows affected is not known, then `execute' returns -1.

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