So far in this chapter, we have discussed only creating tables and adding fields to them. For your tables to be useful, however, they must provide indexes for quickly finding and ordering particular records. Without indexes, it’s necessary to search through each record in the table to find any given value.
A special form of index, the primary key index, serves to uniquely identify each record in the table. You can designate one field or set of fields in a table as a primary key. All values in the primary key must be unique and not Null, and there can be only one primary key for a table.
Another special form of index is the unique index. If you designate one field or combination of fields as a unique index, Microsoft Jet allows only one occurrence of that particular value or combination of values to be entered in your table. The unique index also serves to uniquely identify each record in the table.
This section assumes you know which types of indexes you need, and explains how to build and modify them.
See Also For information about how Microsoft Jet uses indexes for efficient data retrieval, see Chapter 4, “Queries.”