Index only the fields you will regularly use to sort, filter, or search for
data.
Reasons:
a) A table can have only 32 indexes (including any hidden ones.) You will
quickly run out of indexes if you index every field.
b) Access must maintain all those indexes. You will actually slow down data
entry, editing, deletions, action queries, and recordsets with unnecessary
indexes. They also waste memory that could be productively used.
c) Indexes corrupt more frequently than other data: since they are held in
memory using delayed writes, there is a significant chance of a corrupted
index if there is an interrupted write (e.g. network failure, power failure,
hung computer, ...) Therefore unnecessary indexes contribute to unnecessary
corruptions.
