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Home -> Community -> Usenet -> c.d.o.server -> Re: Puzzles on SQL/Oracle
EscVector wrote:
> EscVector wrote:
> > EscVector wrote:
> > > 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.
> > > >
> > > > The intention was a single SQL statement ... I should have written it
> > > > more clearly and for that I apologize.
> > > >
> > > > The point though, much like with new math, is not just to get the right
> > > > answer but to observe how someone approaches the problem.
> > > > --
> > > > 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
> > >
> > > 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"?
> >
> >
> > Here's the plan for my first solution.
> > ------------------------------------------------------------------------------
> > | Id | Operation | Name | Rows | Bytes | Cost (%CPU)|
> > Time |
> > ------------------------------------------------------------------------------
> > | 0 | SELECT STATEMENT | | 40 | 1280 | 12 (84)|
> > 00:00:01 |
> > | 1 | SORT UNIQUE | | 40 | 1280 | 12 (84)|
> > 00:00:01 |
> > | 2 | UNION-ALL | | | | |
> > |
> > | 3 | MINUS | | | | |
> > |
> > | 4 | SORT UNIQUE | | 20 | 320 | 3 (34)|
> > 00:00:01 |
> > | 5 | TABLE ACCESS FULL| A | 20 | 320 | 2 (0)|
> > 00:00:01 |
> > | 6 | SORT UNIQUE | | 20 | 320 | 3 (34)|
> > 00:00:01 |
> > | 7 | TABLE ACCESS FULL| B | 20 | 320 | 2 (0)|
> > 00:00:01 |
> > | 8 | MINUS | | | | |
> > |
> > | 9 | SORT UNIQUE | | 20 | 320 | 3 (34)|
> > 00:00:01 |
> > | 10 | TABLE ACCESS FULL| B | 20 | 320 | 2 (0)|
> > 00:00:01 |
> > | 11 | SORT UNIQUE | | 20 | 320 | 3 (34)|
> > 00:00:01 |
> > | 12 | TABLE ACCESS FULL| A | 20 | 320 | 2 (0)|
> > 00:00:01 |
> > ------------------------------------------------------------------------------
> >
>
>
>> "B"."COL3" IS NULL)
> 4 - filter("A"."COL1" IS NULL OR "B"."COL1" IS NULL OR "A"."COL2" IS
> NULL OR "B"."COL2" IS NULL OR "A"."COL3" IS NULL OR
23:36:10 @splat> 23:36:10 @splat> SELECT 23:36:10 2 A.COL1, 23:36:10 3 A.COL2, 23:36:10 4 A.COL3, 23:36:10 5 'TABLE A' FROM_TABLE 23:36:10 6 FROM 23:36:10 7 TABLE_A A 23:36:10 8 WHERE 23:36:10 9 (A.COL1,A.COL2,A.COL3) NOT IN ( 23:36:10 10 SELECT DISTINCT 23:36:10 11 B.COL1, 23:36:10 12 B.COL2, 23:36:10 13 B.COL3 23:36:10 14 FROM 23:36:10 15 TABLE_B B) 23:36:10 16 UNION ALL 23:36:10 17 SELECT 23:36:10 18 B.COL1, 23:36:10 19 B.COL2, 23:36:10 20 B.COL3, 23:36:10 21 'TABLE B' FROM_TABLE 23:36:10 22 FROM 23:36:10 23 TABLE_B B 23:36:10 24 WHERE 23:36:10 25 (B.COL1,B.COL2,B.COL3) NOT IN ( 23:36:10 26 SELECT DISTINCT 23:36:10 27 A.COL1, 23:36:10 28 A.COL2, 23:36:10 29 A.COL3 23:36:10 30 FROM 23:36:10 31 TABLE_A A); COL1 COL2 COL3 FROM_TA ---- ---------- ---------- ------- a1 1 UNIQUE TABLE A a2 2 UNIQUE TABLE A a3 3 UNIQUE TABLE A a4 4 UNIQUE TABLE A a5 5 UNIQUE TABLE A a6 6 UNIQUE TABLE A a7 7 UNIQUE TABLE A a8 8 UNIQUE TABLE A a9 9 UNIQUE TABLE A a10 10 UNIQUE TABLE A b1 1 UNIQUE TABLE B b2 2 UNIQUE TABLE B b3 3 UNIQUE TABLE B b4 4 UNIQUE TABLE B b5 5 UNIQUE TABLE B b6 6 UNIQUE TABLE B b7 7 UNIQUE TABLE B b8 8 UNIQUE TABLE B b9 9 UNIQUE TABLE B b10 10 UNIQUE TABLE B
20 rows selected.
Elapsed: 00:00:00.03
Execution Plan
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)|
Time |
-------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 40 | 640 | 44 (50)|
00:00:01 |
| 1 | UNION-ALL | | | | |
|
|* 2 | FILTER | | | | |
|
| 3 | TABLE ACCESS FULL| TABLE_A | 20 | 320 | 2 (0)|
00:00:01 |
|* 4 | TABLE ACCESS FULL| TABLE_B | 1 | 16 | 2 (0)|
00:00:01 |
|* 5 | FILTER | | | | |
|
| 6 | TABLE ACCESS FULL| TABLE_B | 20 | 320 | 2 (0)|
00:00:01 |
|* 7 | TABLE ACCESS FULL| TABLE_A | 1 | 16 | 2 (0)|
00:00:01 |
Predicate Information (identified by operation id):
2 - filter( NOT EXISTS (SELECT /*+ */ 0 FROM "TABLE_B" "B" WHERE
LNNVL("B"."COL1"<>:B1) AND LNNVL("B"."COL2"<>:B2) AND
LNNVL("B"."COL3"<>:B3)))
4 - filter(LNNVL("B"."COL1"<>:B1) AND LNNVL("B"."COL2"<>:B2) AND
LNNVL("B"."COL3"<>:B3))
5 - filter( NOT EXISTS (SELECT /*+ */ 0 FROM "TABLE_A" "A" WHERE
LNNVL("A"."COL1"<>:B1) AND LNNVL("A"."COL2"<>:B2) AND
LNNVL("A"."COL3"<>:B3)))
7 - filter(LNNVL("A"."COL1"<>:B1) AND LNNVL("A"."COL2"<>:B2) AND
LNNVL("A"."COL3"<>:B3))
Received on Wed Dec 20 2006 - 22:38:51 CST
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