Basic Computer Notions Databases

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Relational examples (cont'd)

Example relational tables

Question #2: How many babies with birth weights > 2.5 kg have been delivered by each physician?

First we Select babies with BWt > 2.5
B# M# Deliv MWt BWt
941830392382 7512 57.4 3.6
743920392382 7706 58.2 3.4
840238238427 7801 64.1 2.7
230484123456 7803 60.3 3.4
749200649308 7902 58.7 2.9
530284123456 8005 62.3 3.7
638201649308 8101 57.9 3.1

Next we Project the columns we're interested in.

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Last modified: Wed, 2007 Mar 21 17:29:21

Slide show generated from dbms.html by Weasel 2007 Mar 21