Update query from a data file

[Travis]

I've programmed a button on a form to import data from a .csv and put
the information into a table called "tblImportedPrices".

The data being imported is price and performance information for
managed funds.

I have another table, "tblInvestments", which has fields I would like
to update using the data residing in tblImportedPrices.

Both tables share common IDs, the standard industry codes for each
fund. These IDs are unique.

The other information sitting in tblImportedPrices includes fund names,
buy and sell unit prices and performance over various time frames.
There are fields in tblInvestments which I wish to update with this
data.

The values in tblImportedPrices will change as I import different lists
of funds, but the columns will always point to the same types of data.
There will only be limited numbers of funds in the tblImportedPrices
table, I've set it up to get prices only for the funds I'm working with
in that portfolio, so only a minority of funds in tblImportedPrices
will ever be updated in any one update query.

Unless there is data corruption or something, there shouldn't ever be a
fund in tblImportedPrices which isn't in tblInvestments.

First of all, do I set the relationships between tblImportedPrices and
tblInvesments to draw a line between every corresponding field... or
just the common IDs.

And secondly, I can't figure out how to do the update query. I tried a
few things but my skills are not good in this area and I got completely
wrong results.

Any help would be appreciated!

Travis