Help me understanding this Exercise Question This question is from a Book "SQL with and Introduction to PL/SQL by Lannes L. and Morris Murphy. This question is from one of its exercises. I cant understand what this question is asking.


  Q. Determine which books generate less than 55 percent profit and how many copies of those books have been sold recently. Summarize your findings for management and include a copy of the query necessary to retrieve the data from the database tables.


To retrieve the results, Books table joins Orderitems on ISBN and Orderitems joins Orders table on ORDER#

BOOKS TABLE

ISBN       TITLE                               PUBDATE        PUBID       COST     RETAIL CATEGORY
---------- ----------------------------------- --------- ---------- ---------- ---------- ------------------
1059831198 BodyBuilding in 10 Minutes a Day    21-JAN-01          4      18.75      39.95 Fitness
0401140733 Revenge of Mickey                   14-DEC-01          1       14.2         22 Family Life
4981341710 Bulding a Car with Toothpicks       18-MAR-02          2       37.8      59.95 Childern
8843172113 Database Implementation             04-JUN-99          3       31.4      55.95 Computer
3437212490 Cooking with Mashrooms              28-FEB-00          4       12.5      19.95 Cooking
3957136468 Holy Grail of Oracle                31-DEC-01          3      24.25      75.95 Computer
1915762492 HandCranked Computers               21-JAN-01          3       21.8         25 Computer
9959789321 E-Business the Easy Way             01-MAR-02          2       37.9       54.5 Computer
2491748320 Painless Child-Rearing              17-JUL-00          5         48      89.95 Family Life
0299282519 The Wok Way to Cook                 11-SEP-00          4         19      28.75 Cooking
8117949391 Big Bear and Little Dove            08-NOV-01          5       5.32       8.95 Childern
0132149871 How to get Faster Pizza             11-NOV-02          4      17.85      29.95 SelfHelp
9247381001 How to Manage the Manager           09-MAY-99          1       15.4      31.95 Business
2148428890 Shortest Poems                      01-MAY-01          5      21.85      39.95 Literature


ORDERS TABLE

ORDER#  CUSTOMER# ORDERDATE SHIPDATE  SHIPSTREET                SHIPCITY             SH SHIPZ
------- --------- --------- --------- ------------------------- -------------------- -- -----
  1000       1005 31-MAR-03 02-APR-03 1201 Orange Ave           Seattle              WA 98114
  1001       1010 31-MAR-03 01-APR-03 114 East Svannah          Atlanta              GA 30314
  1002       1011 31-MAR-03 01-APR-03 58 Tilla Circle           Chicago              IL 60605
  1003       1001 01-APR-03 01-APR-03 958 Magnolia lane         Eastpoint            FL 32328
  1004       1020 01-APR-03 05-APR-03 561 Roundabout Way        Trenton              NJ 08601
  1005       1018 01-APR-03 02-APR-03 1008 Grand Avenue         Macon                GA 31206
  1006       1003 01-APR-03 02-APR-03 558A Capital Hwy          Tallahassee          FL 32307
  1007       1007 02-APR-03 04-APR-03 9153 Main Street          Austin               TX 78710
  1008       1004 02-APR-03 03-APR-03 69821 Southe Avenue       Boise                ID 83707
  1009       1005 03-APR-03 05-APR-03 9 Lightining Rd           Seattle              WA 98110


ORDERITEMS TABLE

ORDER#      ITEM# ISBN         QUANTITY
----------- ----- ---------- ----------
  1000          1 3437212490          1
  1001          1 9247381001          1
  1001          2 2491748320          1
  1002          1 8843172113          2
  1003          1 8843172113          1
  1003          2 1059831198          1
  1003          3 3437212490          1
  1004          1 2491748320          2
  1005          1 2147428890          1
  1006          1 9959789321          1
  1007          1 3957136468          3
  1007          2 9959789321          1
  1007          3 8117949391          1
I'm not really sure this is truly a DBA question, as it sounds like your problem is understanding the question itself.

The question asks which books generate less than 55% profit. Profit would be the difference between retail and cost. So, the question is, what should the profit be less than 55% of? The basic options are 55% of retail, or 55% of cost. I would assume that retail is intended.

So, you'd need to calculate which books show retail - cost as less than 55% of retail. Then, make a call as to what "recently" means (given orders from just two months, I'd go for all of those orders), and sum the total quantities ordered for each of those books.