Tableau Interview Questions

Monday, 17 March 2014

Tableau Interview Questions -FAQs

Is there any new features implemented in tableau 8.0 regarding the tableau server performance improvement?

1. Use an extract:
2. Limit your dashboard to fully answering only one scenario:
3. Limit the data being introduced to each worksheet:
4. Remove components that add no value:
5. Eliminate any non-essential components from the visualization

What are the other settings I need to reconfigure to get better performance as I am using 7.0 tableau server and planning to upgrade to latest versions?Suggest best configurations based on the provided server details?

Tableau 8,8.1 and 8.2 also supported for 4GB ram and core processors.

How many viz SQL process should I run?

Ddepending on Data Capacity

How many extracts (extract type) can be used on a single server(without effecting server performance like memory) ?

Better 10

What are the possible reasons for slow performance in Tableau?

More Extracts, filters and depends on data sources

How to check the performance step by step manner(DB, Report side, Network) in tableau report ?

Go to help menu and select performance tuning option

How to improve the tableau report performance?

If you are not planning on using a set of rows, you should filter them out of the data set as early as possible. If your table contains all sales, and you only want to look at US sales, create a Custom SQL query that filters it out. If the filter is worksheet dependent, try using a Context Filter. For more information on filtering, check out my other post Types of Filters in Tableau. You can also click the Down Arrow beside the word "Dimension" and Select "Hide All Unused Fields" to hide any fields you are not using in any of your worksheets. I'm not sure if this improves efficiency; but I'd have to imagine that it does, less data should always improve performance.

How we can find the tableau Report Rendering Time.?

Report rendering time=Network time(request from URL to Report server) +Query execution time + Network time(response from SQL Server)+calculations(table column)+time taken to display the report in desired format(html/ pdf/ excel)

What kind of technology is a Tableau Viz?

It is a thin AJAX based JavaScript application

Is there a limit on storage space for the data?

Yes, there is a 1 gigabyte limit on storage space for data. For the vast majority of users, we expect that 1 GB will be more space than needed.

Sunday, 16 March 2014

How do you create dashboard.? Can you explain the life cycle.?

Once we have proper requirement we will create the worksheet in Developer environment and create the dashboard with all the worksheets and then do the unit testing and if everything looks good then we will publish the same in to the dev server with valid permission and the migration will be taken care by our tableau administrator

Can you explain about table calculations?

These are inbuilt calculations in tableau which we normally use to calculate Percentange from or for YTD and other calculations like the measure across table, below table and etc..

I have one scenario like Year in integer and week in String and wanted to calculate the YTD.. how to do this.?

In Tableau, the relative date filter enables flexible analysis of time periods. Sometimes, however, you might want to see both year-to-date (YTD) and month-to-date (MTD) values for a particular measure on the same view. To accomplish this task, you can create date calculations.

Create a calculated column which replaces week from string to integer and make use this in another calculation for YTD.

YTD:

MTD:

What kind of join do you see in data blending?

There won't be any joins as such but we will just give the column references like primary and foreign key relation.

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

Data blending is when you blend data from multiple data sources on a single worksheet. The data is joined on common dimensions. Data Blending does not create row level joins and is not a way to add new dimensions or rows to your data.

We use this when we want to fetch data from different sources and make use in single worksheet.

When do you use horizontal and vertical components?

We can use these when we want to have all sheets or filter to move in single shot.. however we can still create the dashboard without this also.. this allows us to make our work simple

Name the components of dashboard?

Horizontal
Vertical
Text
Images etc

Can we have multiple value selection in parameter?

What are parameters and when do you use it?

Parameters are dynamic values that can replace constant values in calculations.
or
Parameters are used when you want to change the static values.

How to use parameters -1:

How to use parameters - 2:

What is the difference between tableau 7.0 and 8.0 versions

New visualizations are introduced like treemap, bubble chart and box and whisker plot
We can copy worksheet directly from one workbook to another workbook
Introduced R script

Thursday, 13 March 2014

How Does Tableau Work?

While Tableau lets you analyze databases and spreadsheets like never before, you don’t need to know anything about databases to use Tableau. In fact, Tableau is designed to allow business people with no technical training to analyze their data efficiently.

Tableau is based on three simple concepts:

Connect - Connect Tableau to any database that you want to analyze. Note that Tableau does not import the data. Instead it queries to the database directly.
Analyze - Analyzing data means viewing it, filtering it, sorting it, performing calculations on it, reorganizing it, summarizing it, and so on.

Using Tableau you can do all of these things by simply arranging fields of your data source on a Tableau worksheet. When you drop a field on a worksheet, Tableau queries the data using standard drivers and query languages (like SQL and MDX) and presents a visual analysis of the data.
Share - You can share results with others either by sharing workbooks with other Tableau users, by pasting results into applications such as Microsoft Office, printing to PDF or by using Tableau Server to publish or embed your views across your organization.

What is Tableau Reader?

Tableau Reader is a free viewing application that lets anyone read and interact with packaged workbooks created by Tableau Desktop

What is Tableau Server?

Tableau Server is a business intelligence solution that provides browser-based visual analytics anyone can use at just a fraction of the cost of typical BI software. With just a few clicks, you can publish or embed live, interactive graphs, dashboards and reports with current data automatically customized to the needs of everyone across your organization. It deploys in minutes and users can produce thousands of reports without the need of IT services — all within your IT infrastructure.

What is Tableau Desktop?

Tableau Desktop is a data visualization application that lets you analyze virtually any type of structured data and produce highly interactive, beautiful graphs, dashboards, and reports in just minutes. After a quick installation, you can connect to virtually any data source from spreadsheets to data warehouses and display information in multiple graphic perspectives. Designed to be easy to use, you’ll be working faster than ever before.

Tuesday, 11 March 2014

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

Normal Filter:- This is used to restrict the data from database based on selected dimension or measure. If you drag a dimension into filter shelf you can filter the data by selecting list of values. when dragging by measure you can select a range of values.

Quick Filters:- what ever you have applied filter, if you want give a chance to user for dynamically changing data members at run time this is useful. In this you are able to see only non restricted data members only.

OR

The quick filter is a representation of filter to play around and normal filter will not be shown in the workbook to play around.

What is the Difference between connect live and import all data and Import some data.?

Connect live – Creates a direct connect to your data. The speed of your data source will determine performance.

Import all data – Imports the entire data source into Tableau’s fast data engine as an extract. The extract is saved with the workbook.

Import some data – Imports a subset of your data into Tableau’s fast data engine as an extract. This option requires you to specify what data you want to extract using filters.

How do I automate reports using Tableau software?

How does Tableau perform with huge datasets?

How is Tableau so fast when working with databases?

Tableau compiles the elements of your visual canvas into a SQL or MDX query for the remote database to process. Since a database typically runs on more powerful hardware than the laptops / workstations used by analysts, you should generally expect the database to handle queries much faster than most in-memory BI applications limited by end-user hardware. Tableau's ability to push computation (queries) close to the data is increasingly important for large data sets, which may reside on a fast cluster and may be too large to bring in-memory.

Another factor in performance relates to data transfer, or in Tableau's case resultset transfer. Since Tableau visualizations are designed for human consumption, they are tailored to the capabilities and limits of the human perception system. This generally means that the amount of data in a query resultset is small relative to the size of the underlying data, and visualizations focus on aggregation and filtering to identify trends and outliers. The small resultsets require little network bandwidth, so Tableau is able to fetch and render the resultset very quickly. And, as Ross mentioned, Tableau will cache query results for fast reuse.

The last factor as mentioned by Eriglen involves Tableau's ability to use in-memory acceleration as needed (for example, when working with very slow databases, text files, etc.). Tableau's Data Engine uses memory-mapped I/O, so while it takes advantage of in-memory acceleration it can easily work with large data sets which cannot fit in memory. The Data Engine will work only with the subsets of data on disk which are needed for a given query, and the data subsets are mapped into memory as needed.

OR

Tableau does do some amount of in-memory storage to increase speed (when extracted), but a great portion of its speed actually comes from not having to store data in memory.

This is because Tableau only stores the data relevant to your queries in-memory, whereas other solutions will store the entire set in memory, which can take more time to load.

OR

Tableau main feature "data engine" is really a cool feature. If you work with a large amount of data it takes some time to import, create indexes and sort data but after that every thing speedup. Tableau data engine is not really in-memory technology. The data is stored in disk after imported and then RAM is hardly utilized. This conception brings the desired performance.