https://junwu.nptu.edu.tw/dokuwiki/ 2026-04-28T20:40:44+00:00 https://junwu.nptu.edu.tw/dokuwiki/ https://junwu.nptu.edu.tw/dokuwiki/lib/tpl/dokuwiki/images/favicon.ico text/html 2019-07-02T15:01:18+00:00 Anonymous (anonymous@undisclosed.example.com) https://junwu.nptu.edu.tw/dokuwiki/doku.php?id=db:homework:answer1&rev=1562079678&do=diff 作業1 參考解答 (a) create table Product ( maker CHAR(30), model CHAR(10) primary key, _type CHAR(15) ); 註：因dokuwiki排版限制，「type」無法正常顯示，所以使用「_type」代替。 (b) create table PC ( model CHAR(30), speed DECIMAL(4,2), ram INTEGER, hd INTEGER, price INTEGER ); text/html 2019-07-02T15:01:18+00:00 Anonymous (anonymous@undisclosed.example.com) https://junwu.nptu.edu.tw/dokuwiki/doku.php?id=db:homework:answer2&rev=1562079678&do=diff 作業2 參考解答 (e) Find those manufacturers that sell Laptops, but not PC's. (1) Algebraic expression " <latex> \pi_{maker}(\sigma_{type=laptop}(Product) - \sigma_{type=pc}(Product)) </latex>" (2) Linear notation " <latex> R1:= \sigma_{type=laptop}(Product) </latex> text/html 2019-07-02T15:01:18+00:00 Anonymous (anonymous@undisclosed.example.com) https://junwu.nptu.edu.tw/dokuwiki/doku.php?id=db:homework:answer2abc&rev=1562079678&do=diff 作業2 參考解答 page 49, Exercise 4.1 (a) to (c) (a) What PC models have a speed of at least 3.00? (1) Algebraic expression " <latex>\pi_{model}(\sigma_{speed\geq 3.0}(PC))</latex>" (2) Linear notation " <latex>R:=\sigma_{speed\geq 3.0}(PC)</latex> text/html 2019-07-02T15:01:18+00:00 Anonymous (anonymous@undisclosed.example.com) https://junwu.nptu.edu.tw/dokuwiki/doku.php?id=db:homework:answer3&rev=1562079678&do=diff 作業3 參考解答 (a) A PC with a processor speed less than 2.00 must not sell for more than $500. " <latex> \sigma_{speed<2.00 \wedge price>500}(PC)= \emptyset </latex>" (b) A laptop with a screen size less than 15.4 inches must have at least a 100 gigabyte hard disk or sell for less than $1000. text/html 2019-07-02T15:01:18+00:00 Anonymous (anonymous@undisclosed.example.com) https://junwu.nptu.edu.tw/dokuwiki/doku.php?id=db:homework:answer4&rev=1562079678&do=diff The version of the answers is non-redundancy Exercise 3.2.2 (i) S(A,B,C,D) with FD's A->B,B->C,B->D. a. " <latex>A-$>$B,A-$>$C,A-$>$D,B-$>$C,B-$>$D </latex>" b. " <latex>A </latex>" c. " <latex>AB,AC,AD,ABC,ACD,ABD,ABCD </latex>" (ii) T(A,B,C,D) with FD's AB->C,BC->D,CD->A,and AD->B. $>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$$>$ text/html 2021-03-30T04:29:36+00:00 Anonymous (anonymous@undisclosed.example.com) https://junwu.nptu.edu.tw/dokuwiki/doku.php?id=db:homework:start&rev=1617078576&do=diff 國立屏東大學 資訊工程學系 資料庫系統導論 作業及參考解答 * Findkeys * isBCNF * decompose