It’s hard to know for sure exactly how you want to relate them together, but it seems like it could be as simple as using the search parameter on the entries loop. So for example, if both sets of CSV imports are in separate channels, then displaying the two of them that share a unique ID imported as part of their respective data sets could be done like this:
Parent entries loop:
{exp:channel:entries channel="csv_import1" limit="1" dynamic="no" disable="whatever|can|can|live|without"}
{title}
{other_custom_fields_from_csv_import1}
{embed="embeds/csv_import2" the_csv_import1_id="{csv_import1_id}"}
{/exp:channel:entries}
Embed entries loop pulling csv_import2 data in that matches csv_import1:
{exp:channel:entries channel="csv_import2" limit="1" search:cdv_import2_id="={embed:the_csv_import1_id}" dynamic="no" disable="whatever|can|can|live|without"}
{the_custom_fields_from_csv_import2}
{/exp:channel:entries}
Not that I am advocating using embeds, but it’s one quick and simple example of how you might achieve this. You could certainly use the query module to loop through both channels and pull out the custom fields from the two channels with the custom field IDs matching and display them in the template, which would be a more elegant and likely considerably more resource efficient way to achieve what I outlined here.
Hope that helps.