Understanding the 'node' string in a Views SQL Query
The 'node' string is a placeholder of sorts. 

Internally, it indicates to Views that we are not going to attempt to fetch the requested field value in this SQL query itself. Instead, during the Views render process, the full node object is going to be loaded, and the output for that Views field is going to come from partially rendering the node object.

This allows Views to take full advantage of Drupal's field formatting system, which would be impossible on raw SQL values.