Tableau Interview Questions And Answers For 2016


1. What is data visualization?

Data visualization refers to the techniques used to organize and present information intuitively (e.g. points, lines or bars). According to Tableau, using Tableau visualizations, you gain the ability to quickly answer questions; your data becomes a competitive advantage instead of an underutilized asset.

Refer to this blog post for more information.

2. What is the difference between Quick Filter, Normal filter and Context filter?

In Tableau, filters are used to restrict the data from database. The differences between Quick and Normal/ Traditional filter are:

  • Normal Filter is used to restrict the data from database based on selected dimension or measure. A Traditional Filter can be created by simply dragging a field onto the ‘Filters’ shelf.
  • Quick filter is used to view the filtering options and filter each worksheet on a dashboard while changing the values dynamically (within the range defined) during the run time.
  • Context Filter is used to filter the data that is transferred to each individual worksheet. When a worksheet queries the data source, it creates a temporary, flat table that is uses to compute the chart. This temporary table includes all values that are not filtered out by either the Custom SQL or the Context Filter.

3. What is data blending? When do you use this?

According to Tableau, Data blending is the ability to bring data from multiple data sources into one Tableau view, without the need for any special coding.

You can use data blending in Tableau in the following cases:

  • Filter on secondary dimension fields
  • Use secondary dimensions in the view
  • Link data between two data sources using fields that are not in the view

If you are combining data from the same data source, such as Excel worksheets or tables in an Oracle database, you use joining.

4. What are the differences between twb and twbx?

  • A twb is an xml document which contains all the selections and layout made you have made in your Tableau workbook. It does not contain any data.
  • A twbx is a ‘zipped’ archive containing a twb and any external files such as extracts and background images.

5. What is Aggregation & Disaggregation?

The process of viewing numeric values or measures at higher and more summarized levels of the data is called aggregation. When you place a measure on a shelf, Tableau automatically aggregates the data, usually by summing it. You can easily determine the aggregation applied to a field because the function always appears in front of the field’s name when it is placed on a shelf. For example, Sales becomes SUM(Sales).  You can aggregate measures using Tableau only for relational data sources. Multidimensional data sources contain aggregated data only. In Tableau, multidimensional data sources are supported only in Windows. (Source)

According to Tableau, Disaggregating your data allows you to view every row of the data source which can be useful when you are analyzing measures that you may want to use both independently and dependently in the view. For example, you may be analyzing the results from a product satisfaction survey with the Age of participants along one axis. You can aggregate the Age field to determine the average age of participants or disaggregate the data to determine at what age participants were most satisfied with the product.

6. What are the differences between groups and sets?

Groups simplify large numbers of dimension members by combining them into higher-level categories. Sets create a custom field based on existing dimensions that can be used to encode the view with multiple dimension members across varying dimension levels.

7. How do we do testing in Tableau?

You can do performance testing on Tableau with Tableau Server load-testing solution called TabJolt. You can use TabJolt to push a heavy workload onto Tableau Server to give it a jolt and study how the server bends or breaks under load.

You can download TabJolt via GitHub here.

8. What is Pages shelf?

You can analyze data on Tableau using a feature called Pages Shelf. It helps you analyze data based on the individual values contained within a field. For example by adding a date field you can show how your visualization changes over time.

You can find a detailed usage guide for Pages Shelf here.

9. How do you add custom color to Tableau?

Tableau offers three types of color palettes: categorical, sequential, and diverging. You can create your own custom color palette by modifying the Preferences.tps file that comes with Tableau Desktop. The Preferences.tps file is located in the My Tableau Repository. The preferences file is a basic XML file that you can open in a text editor to modify. In tableau 9.0 version there is a color picker option.

10. What is Assume referential integrity?

Referential integrity is a concept which ensures that relationships between databases/tables remain consistent, i.e. it ensures that the references to data are valid. You can improve query performance by selecting this option from the data menu. When you use this option, Tableau will include the joined table in the query only if it is specifically referenced by fields in the view.

11. Explain when would you use Joins vs. Blending in Tableau?

If data resides in a single source, it is always desirable to use Joins.  When your data is not in one place blending is the most viable way to create a left join like the connection between your primary and secondary data sources.

Learn more about Joining Tables and Blending Data here.

12. What is default Data Blending Join?

Data blending is the ability to bring data from multiple data sources into one Tableau view, without the need for any special coding. A default blend is equivalent to a left outer join. However, by switching which data source is primary, or by filtering nulls, it is possible to emulate left, right and inner joins.

13. What do you understand by blended axis?

In Tableau, measures can share a single axis so that all the marks are shown in a single pane. Instead of adding rows and columns to the view, when you blend measures there is a single row or column and all of the values for each measure is shown along one continuous axis. We can blend multiple measures by simply dragging one measure or axis and dropping it onto an existing axis.

More on this topic here.

14. What is story in Tableau?

A story is a sheet that contains a sequence of worksheets or dashboards that work together to convey information. You can create stories to show how facts are connected, provide context, demonstrate how decisions relate to outcomes, or simply make a compelling case. Each individual sheet in a story is called a story point.

15. What is the difference between discrete and continuous in Tableau?

There are two types of data roles in Tableau – discrete and continuous dimension.

  • Discrete data roles are values that are counted as distinct and separate and can only take individual values within a range. Examples: number of threads in a sheet, customer name or row ID or State. Discrete values are shown as blue pills on the shelves and blue icons in the data window.
  • Continuous data roles are used to measure continuous data and can take on any value within a finite or infinite interval. Examples: unit price, time and profit or order quantity. Continuous variables behave in a similar way in that they can take on any value. Continuous values are shown as green pills.

16. How do you automate reports using Tableau software?

This is how you can automate the reports: while publishing the report to Tableau server, you will find the option to schedule reports. Click on this to select the time when you want to refresh the data.

17. How can we combine database and flat file data in Tableau desktop?

You can combine them by connecting data two times, one for database tables and one for flat file. The Data->Edit Relationships. Give a join condition on common column from db tables to flat file

18. What type of join is used in data blending?

No join is used in data blending.

Refer answer to question number 11 for more information.

19. What are the platforms Tableau server can run on?

Tableau server can run on Windows and Mac.

20. Does Tableau integrate with Hadoop/Hive Server?

Tableau can only integrate with Hive Server, not Hadoop.

21. Where all can you use global filters?

Global filters can be used in sheets, dashboards and in stories.

22. How do you publish tableau reports to tableau server?

Tableau reports can be published to server using command utility.

23. How do you normalize data for use in Tableau?

When an Excel data source (other than a cube) is already formatted as a cross-tabulation or is otherwise aggregated, options for viewing, aggregating, and grouping in Tableau are limited. Tableau cannot see underlying data points that have already been summarized into a higher-level group or order. To take advantage of Tableau’s full functionality, you need to normalize the data before connecting to it from Tableau.

You can normalize a table manually, but Tableau provides an Excel add-in that can be downloaded here.

24. What are the new features In Tableau 9.0?

i) Visual Analytics:

a) Type-in shelves

b) Freeform Calculation

c) Drag & Drop Calculation

d) New Calculation Editor

e) Instant reference line & trend line

f) Interactive Table calculation editing

g) Geographic Search

h) Lasso & Radial Selection

ii) Speed (3-4 times faster than current version):

a) Multicore Query Execution

b) Vector Operations Support

c) Parallel Queries

d) Continuous Tooltips

e) Responsive Pan & Zoom

f) Persisted Query Cache

iii) Data Preparation:

a) Unpivoting

b) Web Service API Connector

c) Splitting of Data automatically

iv) Story Telling:

a) Larger Caption

b) Background Colors

v) Enterprise:

a) Provide credentials to different business users on fly

b) Server will be more secure and faster

vi) Cloud:

a) Connect directly with cloud data sources like redshift in Tableau Online

vii) Mobile:

a) A program for mobile users called Project Elastic.

b) It is faster and user friendly

c) You do not need internet connection to run your dashboard on mobile or tablets.

More on this here.

25. Explain and implement a serialization of a binary tree.

You can write serialization for leaf nodes, and then for parent nodes.

Recursive map: {value: [serialize(left), serialize(right)]}, where serialized leaf is null.

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