in reply to Re^4: Can I get the actual error for DBI->execute() ?
in thread Can I get the actual error for DBI->execute() ?

Yes. setting RaiseError => 1 does cause the script to exit immediately, yes?

I prefer to do it that way instead of checking for errors after each DB operation. In your code above, prepare can also throw an error. $dbHandle will be undef if there is an error and you should check for that if you don't set RaiseError.

Note that execute sometimes returns a numerical value that has meaning, like perhaps the number of rows updated. execute behaves differently say for a SELECT statement where no information is provided. So a simple check of $result to detect an error won't work like it does for $dbHandle.

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Re^6: Can I get the actual error for DBI->execute() ?
by Danny (Chaplain) on Jun 23, 2024 at 02:35 UTC
    Marshall wrote: So a simple check of $result to detect an error won't work like it does for $dbHandle.

    I'm pretty sure $sth->execute(...) returns undef if and only if there is an error. From perldoc DBI:

    An "undef" is returned if an error occurs. A successful "execute" always returns true regardless of the number of rows affected, even if it’s zero (see below).

[reply]
      I had to do some review of this because it can get confusing.

      By design you can't get number of rows out of a SELECT statement. You can only get a numerical result out of DELETE or UPDATE statements. The question is how to get that info from Perl DBI? There are 2 ways:

      First with a do statement:
       my $rows = $dbh->do("DELETE FROM table_name WHERE col2='X'");
      $rows can be a) Integer>0 b) 0E0 c) undef
      0E0 is the DB's "true but numeric zero result".
      undef would mean the statement failed.

      Second with prepare/execute:

      my $sth= $dbh->prepare("DELETE FROM table_name WHERE col2=?");
$sth->execute("X");
my $rows = $sth->rows();

      [download]
      $rows can be (like first example): a) Integer>0 b) 0E0 c) undef

      I almost always run with RaiseError=1 so checking for undef doesn't come up.

      I don't know if DBI returns 1 or 0E0 for a successful SELECT operation.

[reply]
[d/l]
[select]
        Marshall write: I don't know if DBI returns 1 or 0E0 for a successful SELECT operation.

        Assuming there wasn't an error, from perldoc DBI: "If the number of rows affected is not known, then "execute" returns -1."

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