Explanation
The INNER JOIN keyword selects all rows from both tables as long as there is a match between the columns.
Consider 2 tables "Orders" and "Customers".
If there are records in the "Orders" table that do not have matches in "Customers", these orders will not be shown!

Explanation
For relational data sources, dates and times are automatically placed in the Dimensions area of the Data pane and are identified by the date or date-time icon. For example, the Order Date and Ship Date dimensions from an Excel data source are shown below:

When you place a relational date on a shelf, the field name is automatically modified to reflect the default date level. Tableau defines the default date level to be the level at which there are multiple instances. For example, if the date field includes multiple years, the default level is year. However, if the date field contains data for just one year but includes multiple months, then the default level is month.

Explanation
THIS IS A VERY IMPORTANT QUESTION
To answer this question, you need to understand Tableau's Order of Operations. See below and remember this always:

Explanation
Follow along to get the correct answer:
* Drag Country to the view, and then Patents to the Size Mark on the Marks shelf as follows :
2) But, this isn't all right? We need to focus on the year 2013. This can be done by using the year column as it is (continuous) in the filter shelf, or by converting it to discrete first and then using it:
2.1 As it is (continuous)

2.2 Converting to discrete first & then using it

and then :

3) We can now see that France, with 485 has the 2nd most number of patents for the year 2013

Explanation
Tree maps size begins from maximum in top left to smallest in bottom right.

See below to learn how to create a TreeMap and add colours to it: