Explanation
You don't need to know ANY programming language to use quick table calculations!
Follow along with the steps below to learn how to apply a quick table calculation to a visualization:
1) Open Tableau Desktop and connect to the Sample-Superstore data source, which comes with Tableau.
2) Navigate to a new worksheet.
3) From the Data pane, under Dimensions, drag Order Date to the Columns shelf.
4) From the Data pane, under Dimensions, drag State to the Rows shelf.
5) From the Data pane, under Measures, drag Sales to Text on the Marks Card.
6) From the Data pane, under Measures, drag Profit to Color on the Marks Card.
7) On the Marks card, click the Mark Type drop-down and select Square.

The visualization updates to look like this:

Apply the quick table calculation
1) On the Marks card, right-click SUM(Profit) and select Quick Table Calculation > Moving Average.
Note: You can only perform quick table calculations on measures in the view.
A delta symbol appears on the field to indicate that a quick table calculation is being applied to the field. The colors in the visualization update to show the moving average of profit across the years.

Explanation
You can union your data to combine two or more tables by appending values (rows) from one table to another.
To union your data in Tableau data source, the tables must come from the same connection.
For example, suppose you have the following customer purchase information stored in three tables, separated by month. The table names are "May2016," "June2016," and "July2016."

A union of these tables creates the following single table that contains all rows from all tables.

Explanation
We need to use the concept of Groups for this question. Follow along:
1) First, Drag State to the Rows shelf, and Total Expenses to the Text Mark on the Marks Shelf:

2) Now, remove the SUM aggregation from Total Expenses, and add a quick table calculation -> Percent of total:

3) Next, Select the States of New York, California and Washington -> And then click the paperclip icon:

We can see the answer already : 23.386% in the view above (even before grouping!)
4) Finally, we get the following view and our answer:

Explanation
Not too tough. Follow along the steps:
* Drag Color to Filter and choose Red:
* 3) Now to display the percentage correctly, lets format it. Click on the In Stock % pill in the Row shelf, and select format:
* And your final view will look like :

Explanation
When you connect to a data source, Tableau automatically separates date fields into hierarchies so you can easily break down the viz. You can also create your own custom hierarchies. For example, if you have a set of fields named Region, State, and County, you can create a hierarchy from these fields so that you can quickly drill down between levels in the viz.