Some Concepts That Underpin GIS - Introducing Geographic Information Systems with ArcGIS - page 25

Garden-Variety Database

Name Occup Pay_Sched

Smith
Jones

Welder
Accountant

Hourly
Bi-Monthly

°

Adams Attorney Monthly

°

°

FIGURE 1-11 Trivial example of a relational database table

Mfgr Num_Doors VIN Color Weight

Porsche 2 123XXX Silver 2300

Porsche 2 887ABC White 2100

Toyota 4 9880123 Grey 2350

Honda 4 456789 Blue 2999

FIGURE 1-12 An RDB of automobiles

All the cells of a given column must contain the same sort of value. Some common ones are as follows:

❏ Character —Any valid ASCII character in a string of almost any length.

❏ Short integer —Can range from slightly less than - 32,000 to slightly more than +32,000.

❏ Long integer —Can range from slightly less than negative two billion to slightly more than positive

two billion.

Floating-point number —Can have an exponent as small as 10 -38 and as large as 10 38 , and you can be
assured of six significant digits of precision.

❏

Double-precision floating-point number —Can have an exponent as small as 10 -308 and as large as 10 308 ,
and you can count on 16 significant digits.

❏

Boolean 22 —A value that is either true or false. ❏

22 Named after George Boole, mathematician (which is why it is not spelled Boolian).