Tableau interview questions and answers for experienced professionals

 

Tableau Interview Questions and Answers for experienced professional

1. What is TABLEAU?

Tableau is the powerful and fastest visualizing tool that is used in the Business Intelligence(BI) Industry. It simplifies the raw data into an understandable format. Analysis of the data becomes faster with Tableau. The visualizations can be created in the form of dashboards. The visualizations or diagrammatic representation of data can easily be understood by the employees of the organizations who are at different levels.

2. List out Tableau File Extensions.

The below ones are few extensions in Tableau:

1. Tableau Workbook (.twb)
2. Tableau Data extract (.tde)
3. Tableau Datasource (.tds)
4. Tableau Packaged Datasource (.tdsx)
5. Tableau Bookmark (.tbm)
6. Tableau Map Source (.tms)
7. Tableau Packaged Workbook (.twbx) – zip file containing .twb and external files.
8. Tableau Preferences (.tps)

Define different connection types in Tableau?

There are 2 connection types available in Tableau.

Extract: Extract is a snapshot of data that will be extracted from the data source and put into the Tableau repository. This snapshot can be refreshed periodically fully or incrementally. This can be scheduled in Tableau Server

Live: It creates a direct connection to the data source and data will be fetched directly from tables. So, data will be up to date and consistent. But, this also affects access speed.

Define fact and dimensions?

Facts are numeric measures of data. They are stored in fact tables. Fact tables store that type of data that will be analyzed by dimension tables. Fact tables have foreign keys associated with dimension tables.

Dimensions are descriptive attributes of data. Those will be stored in the dimensions table. For example, customers’ information like name, number, and email will be stored in the dimension table.

What are the different Joins in Tableau?

Tableau works the same as SQL. So, it supports all Joins possible in SQL

• Left Outer Join
• Right Outer Join
• Full Outer Join
• Inner Join

What is Tableau Reader?

Tableau Reader is a free desktop application, where you can read and interact with the Tableau packaged workbooks. It can only open the files but cannot create new connections to the workbook.

Define Page Shelf in Tableau?

Page shelf breaks the views into a series of pages. It displays an alternate view on each page. Due to this feature, you can analyze the effect of each field on the rest of the data in the view.

What is published data and embedded data sources?

The published data source contains connection information that is independent of workbooks and can be used by multiple workbooks.

The embedded data source contains connection information but it is associated with the workbooks.

Differentiate parameters and filters in Tableau

Filters are the simpler and straightforward feature in Tableau. It applies to dimensions or measures directly. For example, to only show Gujarat or Karnataka in a State dimension, we can apply the filter on that. In Tableau, there are multiple UI options available for filters like radio buttons, drop-down lists, checkboxes, sliders, and more. Filters on sheets are also available in Tableau.

Parameters are like variables. They are complex and more powerful. Like a variable, a parameter can be used in calculations. So, that means, it only allows a single value. Parameters have the same UI options except for checkboxes because checkboxes don’t have a single value. For example, we can create a parameter for interest rate and period, and then we can use these parameters to calculate interest and principal payments.

Different types of filters are available in Tableau?

Filters are used to provide the correct information to viewers after removing unnecessary data. There are various types of filters available in Tableau.

Extract Filters – Extract filters are used to apply filters on extracted data from the data source. For this filter, data is extracted from the data source and placed into the Tableau data repository.

Datasource Filters – Datasource filters are the same as extract filters. They also work on the extracted dataset. But, the only difference is it works with both live and extract connections.

Context Filters – Context Filters are applied on the data rows before any other filters. They are limited to views, but they can be applied on selected sheets. They define Aggregation and Disaggregation of data in Tableau

Dimension Filters – Dimension filters are used to apply filters on dimensions in worksheets. Dimension filters are applied through the top or bottom conditions, formula, and wildcard match.

Measure Filters – Measure filters are applied to the values present in the measures.

Differentiate between Tiled and Floating in dashboards?

In a tiled layout, items don’t overlap. The layout will be adjusted according to dashboard size. In the floating layout, items can be placed on some other layers. Floating items can have fixed positions and sizes.

What is Data Modelling?

Data modeling is the analysis of data objects that are used in a business or other context and also used as identification of the relationships among these data objects. It is the first step of doing object-oriented programming.

Differentiate discrete and continuous data roles in Tableau

Discrete data roles consist of values that are separate and distinct. Discrete data roles can take individual values within a range. For Example – cancer patients in the hospital, no. of threads in a sheet, state. Discrete values are displayed as blue icons in the data window and blue pills on shelves. Discrete fields can be sorted.

Continuous data roles consist of any value within the finite or infinite intervals. For Example – age, unit price, order quantity. Continuous values displayed as green icons in the data window and green pills on shelves. Continuous fields cannot be sorted.

Extract or Live connection, which one is better?

Extract connection is better than live connection because extract connection can be used from anywhere, anytime without connecting to the database. We can construct our own visualizations on it irrespective of the database connection.

What are Calculated Fields?

A Calculated Field is a user-created field that can include operations on other fields that are present in the data. A calculated field does not impact the original data but rather creates a new field that contains the results of the operations conducted on the data.

What is the difference between a TWB and a TWBX file?

A TBW file is the basic Tableau file, which contains instructions regarding how Tableau interacts with a particular source of data. However, the data source needs to be attached separately and placed at an appropriate location for Tableau to interact with it. A TWBX file is a Tableau package, which contains the entirety of the data to be analyzed as well as the analysis.

What is a blended axis?

Very often, in Tableau, you may need to present multiple graphs in the same Cartesian plane. These graphs may have to be derived from different measures. You can do so with a blended y-axis. The caveat to incorporating a blended axis is that the unit and scale of the two measures must be the same.

What are Groups in Tableau?

A Group in Tableau is a collection of categories that can be used to create a single overarching subcategory. An example can be considered from the Superstore data set, in which several different product subcategories are present. You can create a group of any number of these subcategories and create a single category for analysis.

What is the difference between a Heat map and Treemap?

TreeMap Heat MapIt represents the data hierarchically and shows them as a set of nested rectangles. It represents the data graphically which uses multiple colors to represent different values. It is used for comparing the categories with colors, size, and it can also be used for illustrating the hierarchical data and part to whole relationships. It is used for comparing the categories based on color and size. And also it is great in spotting the patterns based on the density of the information. The colors and size of rectangles are respective to the values of the data points When their values are higher or density of records, the data will represent in dark color.

Define some ways to improve the performance of Tableau

• Use an Extract to make workbooks run faster
• Reduce the scope of data to decrease the volume of data
• Reduce the number of marks on the view to avoid information overload
• Try to use integers or Booleans in calculations as they are much faster than strings
• Hide unused fields
• Use Context filters
• Reduce filter usage and use some alternative way to achieve the same result
• Use indexing in tables and use the same fields for filtering
• Remove unnecessary calculations and sheets

Define Dual-axis?

Dual-axis is used to show 2 measures in a single graph. It allows you to compare 2 measures at once. 

What is context filters in Tableau?

Whenever we set a context filter, Tableau generates a temp table that needs to refresh each and every time, whenever the view is triggered. So, if the context filter is changed in the database, it needs to recompute the temp table, so the performance will be decreased.

Define LOD Expression?

LOD Expression stands for Level of Detail Expression, and it is used to run complex queries involving many dimensions at the data sourcing level.