[thelist] Shell Script Basics?

rudy r937 at interlog.com
Wed May 23 15:09:25 CDT 2001

>(Well, almost. They ain't got no books on wimmen....)

yeah, that one ain't been written yet

i can contribute several chapters, though, except they won't do anybody any
good except me, and for me any advice along those lines is already too
little too late...

a many-to-many database relationship is best visualized as two intersecting

skill -- person is 1-m
a skill may be possessed by several persons

person -- skill is 1-m
a person may possess several skills

the intersection is implemented in a "relationship" or "intersection" table
(a "junction" table in the old codasyl network database terminology)

the intersection table, personskill, is a child of both the skill table and
the person table simultaneously

add some skills
 01 html
 02 javascript
 03 css
 04 cf
 05 sql

add some persons
 934 joe
 935 fred
 936 mary
 937 rudy

add some personskills
 934 01
 934 03
 936 04
 937 04
 937 05

list the skills of a particular person
 select skillname
    from person join personskill join skill
   where personid=937

list the persons who have a particular skill
 select personname
   from skill join personskill join person
    where skillid=03

finding people who have a particular *set* of skills (e.g. 03 *and* 04) is
a little trickier but still straightforward (it involves subselects)



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