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Home -> Community -> Usenet -> c.d.o.server -> Re: Puzzles on SQL/Oracle
DA Morgan wrote:
> Charles Hooper wrote:
> > DA Morgan wrote:
> >> EscVector wrote:
> >>> On Dec 18, 1:52 pm, DA Morgan <damor..._at_psoug.org> wrote:
> >>>> Assume two identical tables, one named "A" the other "B" with
> >>>> identical column definitions. Assume that some rows in "A" are
> >>>> duplicated in "B" and some in "B" are duplicated in "A" but each
> >>>> table contains rows unique to that table.
> >>>>
> >>>> Write a single SELECT statement that will retrieve all of the rows
> >>>> from table "A" that are unique to "A", all the rows from "B" that
> >>>> are unique to "B" and label each retrieved row with the name of
> >>>> the table in which it was found.
> >>>>
> >>>> Have fun (and yes there are multiple solutions).
> >>>> --
> >>>> Daniel A. Morgan
> >>>> University of Washington
> >>>> damor..._at_x.washington.edu
> >>>> (replace x with u to respond)
> >>>> Puget Sound Oracle Users Groupwww.psoug.org
> >>> CREATE TABLE A
> >>> ( COL1 CHAR(4),
> >>> COL2 NUMBER,
> >>> COL3 VARCHAR2(10));
> >>>
> >>> begin
> >>> for x in 1..10
> >>> loop
> >>> insert into a values ('ab'||x, x,'NONUNIQUE');
> >>> end loop;
> >>> end;
> >>> /
> >>>
> >>> create table B as select * from a;
> >>>
> >>>
> >>> begin
> >>> for x in 1..10
> >>> loop
> >>> insert into a values ('a'||x, x,'UNIQUE');
> >>> end loop;
> >>> end;
> >>> /
> >>>
> >>> begin
> >>> for x in 1..10
> >>> loop
> >>> insert into a values ('b'||x, x,'UNIQUE');
> >>> end loop;
> >>> end;
> >>> /
> >>>
> >>> commit;
> >>>
> >>> (select a.col1 ,a.col2 ,a.col3, 'TABA' from a minus select
> >>> b.col1,b.col2,b.col3, 'TABA' from b )
> >>> union
> >>> (select b.col1,b.col2,b.col3 ,'TABB' from b minus select
> >>> a.col1,a.col2,a.col3 ,'TABB' from a );
> >> I'll just offer one, minor, critique.
> >>
> >> Given that the two SELECT statements must be obtaining different
> >> results, and no overlap is possible, UNION ALL would be more
> >> efficient.
> >>
> >> How about a second solution? Or a third? <g>
> >> --
> >> 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
> >
> > This is not a comment against EscVector...
> >
> > I wonder if I would have passed this exam, had this been the only
> > question on the exam. Quoting: "Write a single SELECT statement that
> > will retrieve all of the rows..." I counted four SELECT statements in
> > the answer provided by EscVector. Was the requirement a single SQL
> > statement? Did I misunderstand the question?
> >
> > Charles Hooper
> > PC Support Specialist
> > K&M Machine-Fabricating, Inc.
>
>
Not that I could do better, but I put this out there on purpose. I figured you meant use only one Select in the SQL statement, but I posted the first thing that came to mind. The rational is that it is a "single" non-procedural SQL statement. :) I used multiple selects in one statement. You were asking for a single select in one statement. I'd like to add a bonus question: Which is the optimal statement?
"Get it done or Make it Perform". The typical approach is as I have posted; get it done. Performance always comes second. Prereq: clarify the work before investing effort. Since I did the fastest thing I could with almost zero effort, you were able to clarify the work for me while I ate dinner :) Is this what they call "agile"? Received on Wed Dec 20 2006 - 21:46:48 CST
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