Re: SQL sort

[Charles Wilt <charles.wilt@xxxxxxxxx>]

Originally IBM recommend specifying the physical...

As I understand it, originally it worked like so:
 - if you had a select/omit logical that for example selected records where
myfld=1
 - you did a SELECT * FROM MYLF
 - the SQE had to examine MYLF and would rewrite(?) the query as SELECT *
FROM MYPF WHERE MYFLD=1.
     (or perhaps drop into CQE?)

Anyway there was extra work involved...

Now however, the SQE has advanced such that using a LF isn't detrimental
and could in fact help.

Charles

On Thu, Sep 3, 2015 at 4:28 PM, Alan Shore <ashore@xxxxxxxx> wrote:

> Hi Booth
>
> I understand and agree with your comment about your biggest problem being
> that you haven't yet figured out how to ask the right questions.
>
> I have been using SQL for quite a few years now - and I STILL not yet
> figured out how to ask the right questions.
>
> When I first started using SQL - I was told - ALWAYS use the physical with
> your selects (or omits) within the SQL script (although I could never find
> out why)
>
> I followed this directive UNTIL I had to run one particular (relatively
> simple) SQL script.
> It gave me the answers I was looking for - but it took a rather long time
> to run - 20 minutes or so - a LARGE file
> So just for the hell of it, I changed the script to use a logical (for the
> selects and omits) and it literally took seconds - with the same results
>
> Nowadays - I still tend to use the physical - but I keep the idea of using
> a logical in the back of my head
> Alan Shore
> E-mail : ASHORE@xxxxxxxx
> Phone [O] : (631) 200-5019
> Phone [C] : (631) 880-8640
> 'If you're going through hell, keep going.'
> Winston Churchill
>
> -----Original Message-----
> From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of
> Booth Martin
> Sent: Thursday, September 03, 2015 4:15 PM
> To: Midrange Systems Technical Discussion
> Subject: SQL sort
>
> I am fairly new with SQL so please excuse what are most likely very simple
> questions.
>
> I am  looking to understand the pros and cons with SQL.
> On large files with data that will be used in various applications and in
> various sort-by schemes, are logical files a help?
> If so, does one reference the physical file and then SQL finds the best
> logical, or does it help to specify a specific logical file?
> What is the right way to collect a set of records equal to SFLPAGE?
>
> So far, I believe my biggest problem is that I haven't yet figured out how
> to ask the right questions.
>
>
> --
> Booth Martin
> www.martinvt.com
> (802)461-5349
>
> If the world comes to an end, I want to be in Cincinnati. Everything
> comes there ten years later. -- Mark Twain
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