Re: Indexing questions: Index == key? And index vs substring - how successful?

> 1. Does an indexed column on a table have to be a potential primary
> key?

Nope, create as many index as you need/must/should.

> I've been working with a couple of rather large tables where a common
> select is on a foreign key called 'cntrct_id' (Varchar(9) in format).
> However, the same 'cntrct_id' can appear on multiple records in the
> tables I'm trying to work with now; the tables themselves record events
> associated with the given 'cntrct_id' record and can store many events
> for one 'cntrct_id' value. I'd thought that creating an index on the
> table.cntrct_id field for the event tables would allow me to speed up
> the transations some, but comparisons of time before and after the
> indexing lead me to wonder if I was mistaken in this. The times were
> almost identical in the following areas: Before Indexing, after Indexing
> but before Analyzing, and after Analyzing.
> 2. Another common sort on these fields uses part, not all, of the
> 'cntrct_id' value to search for things; the first character marks
> original location in an internal framework we're using, for example, and
> the third character marks the month of the year that the original
> 'cntrct_id' record was set up. Sorts on either of those are fairly
> common as well; would indexing on the cntrct_id as a whole be able to
> speed up a sort on a portion of it?

Nope.
This looks like suboptimal schema design...
If you had an indexed date column, you would be able to make fast indexed
queries with BETWEEN, >=, <=, etc.