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Chapter 10: Practical Database Design Methodology and Use of UML Diagrams

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CHAPTER 10: PRACTICAL DATABASE DESIGN METHODOLOGY AND USE OF UML DIAGRAMS 10.22 -

What are the current relational DM!s that dominate the mar"et# Pic" one that you are familiar $ith and sho$ ho$ it measures up based on the criteria laid out in !ection 10%&%'#  Answer:

Current popular relational DM!s ()DM!s* include D& and +nformi, Dynamic !erer (from +M*. /racle and )db (from /racle*. and !L !erer and ccess (from Microsoft*% !ome other commercial relational DM!s used are !ybase (also "no$n as !ybase !L !erer*. Parado,. and 2o,base% )ecently. some open source relational DM!s. such as My!L. Post3re!L. and 2ireird. hae also gro$n in popularity% t the time this solution $as $ritten. the mar"et share aried depending on platform4 $ith D&. /racle. and Microsoft !L !erer dominating the mar"et oerall% !pecific criteria ealuation $ould depend on the database chosen% 10.23  -

 possible DDL corresponding corresponding to 2igure '%1 is sho$n belo$: C)565 6L5 !6UD576 ( 7M5 8)C9)('0* 7/6 7ULL. !! 7 C9)(* P)+M); uestion '%1% Copyright © 2011 Pearson Education, Inc. Publishing as Pearson Addison-Wesley.

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Chapter 10: Practical Database Design Methodology and Use of UML Diagrams

6he same reasoning can be applied to the 9omephone and /fficephone fields. brea"ing them into multiple fields such as reaCode. Phone7umber. 5,tension. etc%  nother possible modification is to increase the si?e of the 9omephone. /fficephone. and !!7 fields so that formatting characters can be entered. such as !!7 becoming a 8)C9)(11* to allo$ for the t$o dashes in BBB-;;-% 6he table design allo$s for t$o phone numbers. 9omephone and /fficephone. either  of $hich may be 7ULL% 6his means that some ro$s $ill hae empty fields for those attributes%  solution is then to add a Phone (!!7. 6ype. 7umber* table and remoe the t$o phone number fields from the !tudents table% 6his allo$s for any student to hae ?ero or more phone numbers of arious types. $hich $e can specify (9ome. /ffice. Cell. etc%*% Consider not storing the 35 data and instead storing Date/firth% 6ypically only the year component of ge is stored $hich is less accurate than if Date/firth $ere stored and the age computed from it% 6hat is. $e can generate ge from Date/firth. but $e cannot generate Date/firth from ge% e*  suggested constraint is on the 3P field. to restrict its alues from 0%000 to =%000% 6his $ould. ho$eer. preent the (rarely seen* 10 or 1& point grade scale% nother possible constraint is to limit ge to be from 0 to 100 (or een a lo$er ma,imum alue*%

10.24  -

What naming conentions can you deelop to help identify foreign "eys more efficiently#  Answer:

6he naming conention can be informally specified as 2< follo$ed by the referenced relationship or relation name. and optionally follo$ed by the primary "ey of the referenced table% 6his foreign "ey naming conention is fre>uently used in large databases% !ometimes this produces ery long column names but it pays off by facilitating readability for database professionals by using more descriptie names%

Copyright © 2011 Pearson Education, Inc. Publishing as Pearson Addison-Wesley.