FIGURE 7.1. Simplified representation showing the most common types of databases for GI and maps and the important difference between flat-file and relational database types of organization. From A Primer of GIS, 2nd edition, by Francis Harvey. Copyright 2016 by The Guilford Press.

FIGURE 7.2. Database table relates (or joins) are made by identifying the same attributes in the key fields from two separate tables. In this example, the FIPS code can be used to relate population data to the corresponding counties. From A Primer of GIS, 2nd edition, by Francis Harvey. Copyright 2016 by The Guilford Press.

FIGURE 7.3. Highway and major road network in the Twin Cities, Minnesota, United States. The map on the left shows the roads without symbols. Storing or calculating the symbol values from database fields or sensor input help reliably communicate traffic conditions. From A Primer of GIS, 2nd edition, by Francis Harvey. Copyright 2016 by The Guilford Press.

FIGURE 7.4. Examples for symbols used in classifying roads in the United States. The use of conventional symbology and storage of the corresponding data helps to ensure reliable communication with the maps created from this data. From A Primer of GIS, 2nd edition, by Francis Harvey. Copyright 2016 by The Guilford Press.

FIGURE 7.5. Examples of proper field length (top); too short field length (middle); too long field length (bottom). From A Primer of GIS, 2nd edition, by Francis Harvey. Copyright 2016 by The Guilford Press.

FIGURE 7.6. Entity-relationship (E-R) diagram. From A Primer of GIS, 2nd edition, by Francis Harvey. Copyright 2016 by The Guilford Press.