how to get the ordinal number in list

[Chris Angelico]

On Wed, Aug 13, 2014 at 11:45 AM, Roy Smith <roy at panix.com> wrote:
> In article <mailman.12903.1407893523.18130.python-list at python.org>,
>  Chris Angelico <rosuav at gmail.com> wrote:
>
>> I like to look at SQL as a language that specifies an end result
>> without specifying how to get there
>
> Well, sure, but sometimes the how to get there is a matter of 10x, or
> 100x, or 1000x in performance.

Of course it can! But generally, the "how to get there" is not
stipulated in the SQL statement. If you say, for instance:

select * from some_table where some_column='some_value';

then an index on some_column will make a huge difference to
performance - without changing this statement at all. In contrast,
taking advantage of an index in BTrieve requires recoding your
program, as the index used is a part of the API call. (At least, this
is true of the particular version of BTrieve that back-ended our
accounting package in the 90s. I was able to turn an overnight job
into a thirty-second job by rewriting it as an external program; the
original is closed-source so I can't be sure, but I suspect most of
that improvement is simply because I used an index.)

SQL itself doesn't even have provision for indexes. The 'CREATE INDEX'
command, found in many databases, is an extension. :)

ChrisA