Deriving Information by Combining Tables
Add Soils to the map. Drag it to the bottom of the Table of Contents. Look at the Soils attribute table. Write the names of the fields in Attributes of soils.
___________, _______________, _______________,
Note that, just from this table, you have no way of knowing which of the 20 polygon areas consist of sand. However, each polygon does have a value in a SOILS_ID field. This field will allow you to key into a second table that matches up the values of SOIL_ID with a similar field in another table.
In the PGDB_GOLD.mdb database, you will find a table named soil_type. Add that to the Table of Contents and open it. What fields do you find?
_______________, _______________, _______________
Close all attribute tables.
Here are some salient facts:
- The values in the field SOILS_ID (in soil_type) correspond to the values in SOILS_ID (in the Soils feature class). Each is a key field in its table.
- A key field contains, for each record, a unique value that identifies that record.
- A given value in the SOILS_ID field in the soil_type table refers to a polygon with the same number in the SOILS_ID in the attribute table.
- When a table B is joined to a table A, the records of table B are concatenated with the records of table A based on the identical values in the key fields.
- Joining the soil_type table to the Soils feature class table, using the keys, will result in associating the correct ...