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:
- Tableau Workbook
(.twb)
- Tableau Data extract
(.tde)
- Tableau Datasource
(.tds)
- Tableau Packaged
Datasource (.tdsx)
- Tableau Bookmark
(.tbm)
- Tableau Map Source
(.tms)
- Tableau Packaged
Workbook (.twbx) – zip file containing .twb and external files.
- 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.
