Re: SQL Question (selection by RRN)

["R. Bruce Hoffman, Jr." <rbruceh@xxxxxxxxxxxxx>]

-----Original Message-----
From: Stone, Brad V (TC) <bvstone@taylorcorp.com>
To: 'MIDRANGE-L@midrange.com' <MIDRANGE-L@midrange.com>
Date: Tuesday, December 12, 2000 5:50 PM
Subject: SQL Question (selection by RRN)


>i'm playing with SQL, and I was under the assumption that when you select
by
>RRN that it should be very fast.  I'm finding that isn't the case.
>
>Any ideas?  I'm doing something like:
>
>SELECT CHAR(A.ODPERDSC) FROM CSODATA/OCSDETAIL A WHERE
> RRN(A) = 84201 FOR READ ONLY OPTIMIZE FOR 1 ROWS
>
>Takes a while.  (File is very large).   In other cases I've had great
>results.  Shouldn't RRN selection be BAM! right there?


You would think, wouldn't you? But note that RRN(correlation_name) is a
function. It is computed. So the request does a table scan and looks up the
RRN.

Direct access (which is what you are asking for) is not really defined in a
relational database. It was a side-affect in ISAM databases.

Also, note that when you create a table using SQL, the default is to re-use
deleted records. So a record that is in position 12 now, might not be later.

===========================================================
R. Bruce Hoffman, Jr.
 -- IBM Certified Specialist - AS/400 Administrator
 -- IBM Certified Specialist - RPG IV Developer

"Those who would give up essential Liberty,
  to purchase a little temporary Safety,
  deserve neither Liberty nor Safety."

     - The Papers of Ben Franklin



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