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Refer to the example in my answer to http://drupal.stackexchange.com/questions/152166/fetching-drupal-articles-tags-image-directly-from-database/154746#154746 to get an idea of what it is like to use Forena, such as the SQL query and the source of the "custom report", which looks like so:

Disclosure: I'm a co-maintainer (not owner ...) of this module,
I hope this does not violate the site's policy on self-promotion.

Refer to the example in my answer to https://drupal.stackexchange.com/questions/152166/fetching-drupal-articles-tags-image-directly-from-database/154746#154746 to get an idea of what it is like to use Forena, such as the SQL query and the source of the "custom report", which looks like so:

Disclosure: I'm a co-maintainer (not owner ...) of this module,
I hope this does not violate the site's policy on self-promotion.

The Forena module is another option to consider. It comes with quite some community documentation.

Disclosure: I'm a co-maintainer of this module,
I hope this does not violate the site's policy on self-promotion.

Moreover, the title of this question (= "Use Views or Write Raw Query?") sounds to me that you might be interested in learning about other options available, different from using the views module. If that's the case, then the Forena module is another option to consider. It comes with quite some community documentation. And "Write Raw Query" is exactly one of the things you would use Forena for (i.e. what in forena is called 'data blocks').

Disclosure: I'm a co-maintainer (not owner ...) of this module,
I hope this does not violate the site's policy on self-promotion.

Forena is built of the idea of using SQL to get data out of a database (which can be the Drupal database or an external one such as My SQL, Oracle, MS SQL, ...) and use XHTML and CSS to format it into web reports. There are quite some reasons for considering Forena (which also explains how "Forena complements the views module", suggested in some other answers here also). Visit the Forena HowTos page for some links (near the bottom) to some live demo / showcase links.

Forena is built of the idea of using SQL to get data out of a database (which can be the Drupal database or an external one such as My SQL, Oracle, MS SQL, ...) and use XHTML and CSS to format it into web reports. There are quite some reasons for considering Forena, which also explains how "Forena complements the views module" (suggested in some other answers here also), i.e.:

• "Why not use views instead of forena?" ... The answer is generally something along the lines of "Most forena users love views, views is great! If you want to report against external data though, or you want to do aggregation or analytics, Forena is much more suited to address these requirements."
• "What does it take to create reports / charts with the typical Business Intelligence tools? Where would I start in case such reports are to be shown on a Drupal site ... and the actual data may either come from any of Drupal's own tables, or in a PDO-style external database, or some XML or CSV file?" ... Trying to answer these questions leads to more questions such as "How far can you get (and what would it take to get there) with the views module (not even talking about how to secure the access to such data)?

Visit the Forena HowTos page for some links (near the bottom) to some live demo / showcase links.