Aside from the mandatory tables, optional tables may be added and used to store information such as
geology and assays.
There are three different types of optional tables that can be added to a database:
1. Interval(depth from and depth to)
2. Point(depth to)
3. Discrete(point data)
Interval tables require the depth at the start of the interval and the depth at the end of the interval,
called the depth_from and depth_to fields respectively.
Point tables require only the depth where the sample was taken, called the depth_to field. A sample
identifier field is defined for interval tables but this is not a key field and so does not require data if it is
not available. The y, x and z fields are used to store the calculated coordinates of the sample depths.
Discrete sample tables are used for storing data for a point, which has a unique samp_id. All that is
required for this table is the samp_id and its position in space i.e. its Y, X and Z coordinates. The discrete
sample table is ideally suited for storing and later processing geochemical soil samples