Re: Puzzles on SQL/Oracle

DA Morgan wrote:
> > What I was looking for when I started building the second example was a
> > way to retrieve the binary values of all columns in a row (ragardless
> > of the column names), pass the binary values through DBMS_CRYPTO.HASH
> > to generate a hash key, and then use that to see if two rows resolved
> > to exactly the same hash key. I didn't find the function that I was
> > searching for to pull the binary values of all columns. Something like
> > this, but without listing each of the columns:
> > SELECT
> > NVL(A.COL1,B.COL1) COL1,
> > NVL(A.COL2,B.COL2) COL2,
> > NVL(A.COL3,B.COL3) COL3,
> > NVL2(A.COL1,'TABLE A','TABLE B') FROM_TABLE
> > FROM
> > TABLE_A A
> > FULL OUTER JOIN
> > TABLE_B B ON A.COL1=B.COL1 AND A.COL2=B.COL2 AND A.COL3=B.COL3
> > WHERE
> >
> > DUMP(A.COL1||'^'||A.COL2||'^'||A.COL3)<>DUMP(B.COL1||'^'||B.COL2||'^'||B.COL3);
> >
> > Charles Hooper
> > PC Support Specialist
> > K&M Machine-Fabricating, Inc.
>
> I personally like the question because, as I stated before, it allows
> the interviewer to really get a sense of someone's skills as well as
> how they approach a problem.
>
> Other approaches I've seen include an INTERSECT or INNER JOIN and then
> filtering out anything in the intersection.
> --
> Daniel A. Morgan
> University of Washington
> damorgan_at_x.washington.edu
> (replace x with u to respond)
> Puget Sound Oracle Users Group
> www.psoug.org

There are a lot of variants - I agree that it is a good question. I posted a couple solutions that used an ANSI FULL OUTER JOIN, a couple that used INTERSECT, another that used NOT IN, another using an inline view and left outer joins (simulating the NOT IN, just more efficient on older versions of Oracle), and even one that used an analytic function. EscVector posted a method using MINUS syntax. I am sure that there are still methods ways.

Is there no method of retrieving the byte values of all columns in a row without listing the column names?

Charles Hooper
PC Support Specialist
K&M Machine-Fabricating, Inc. Received on Thu Dec 21 2006 - 18:56:16 CST