Often, data used in a spatial database is imported from other sources. As such, it may not be in a form that is useful for our current application. In such a case, it may be useful to write functions that will aid in transforming the data into a form that is more useful for our application. This is particularly the case when going from flat file formats, such as shapefiles, to relational databases such as PostgreSQL.

There are many structures that might serve as a proxy for relational stores in a shapefile. We will explore one here: a single field with delimited text for multiple relations. This is a not-too-uncommon hack to encode multiple relationships into a flat file. The other common approach is to create multiple fields to store what in a relational arrangement would be a single field.