How to display data from external tables in Drupal without coding? I want Drupal users to be able to display data from external databases. There is no processing involved, just listing the results based on filters. What Drupal 7 techniques are capable of accomplishing this?

I am not interested in anything that requires coding, just using the admin modules. A little coding at the start to configure access to the external databases is fine, but the main linking and displaying shouldn't require coding.
Have a look at the Forena module. You would use its report writing features (such as its WYSIWYG report writer and/or it's query builder) to first create a report that fits your needs. The result of it could be a tabular output and/or graph. After the report content matches the specifications, you could save it as (e.g.) a CSV file.

Samples


Refer to this online example in the Forena demo site for a report you could (easily) create:


Using Forena's Query builder you would create the required SQL statement (if you'd rather want to write the SQL with your favorite SQL editor that's another option).
Using forena's WYSIWYG report writer you would develop your custom report (if you'd rather want to write that report with your favorite XHTML editor that's another option).


Some more details about the sample report mentioned above:


Use the "Parameters" pulldown option, to select any other state.
Note the PDF hyperlink: using that link, you'll get a PDF version of that report. When creating such report, you could as well ask for other (or additional) report export formats, one of them is CSV (or XLS, DOC, HTML, ...). This is how the CSV equivalent version of that sample report looks like.

The Master Summary with drill down sample report demonstrates how you can also "link" various reports together (while it also shows some of the charting features of Forena). Click on either any of those bars in the chart, or on the total-hyperlink in tabular report below the chart. Doing so will bring you to the report "for the selected state" (= the first sample report mentioned above).


Direct access to data blocks

All data blocks are accessible directly via their url also, provided you have permission to access that block. Here are a few samples of that, for the sample report located at /reports/sample.states:


in XML format (= demo with anonymous access).
in JSON format (= demo with anonymous access).
in XML format (= demo without anonymous access).
in JSON format (= demo without anonymous access).


Video tutorials

The Forena Video demos and tutorials contain quite some links to live demos. They should help a lot to get you started.

Disclosure: I'm a co-maintainer of Forena.