Tableau Interview Questions, Study notes of Acting

Download Tableau Interview Questions and more Study notes Acting in PDF only on Docsity! Tableau Interview Questions 1.Difference between tableau extensions .twb and .twbx. Twbx: 1. .twbx file is a Tableau Packaged Workbook, meaning it is the original .twb file groupedtogether with the datasource(s) in one package. 2. .twbx files can be considered analogous to specialized zip files, in which these“zip” files contain all the information necessary to work in Tableau. 3. The primary advantage to using .twbx files is that analysis can be performed withoutnetwork/internet connections to your data because your data is already present on yourcomputer in this packaged file. Twb: 1. The .twb file alone is not enough to perform any analysis because it only containsTableau’s instructions for interacting with a datasource. 2. In actuality, .twb files are XML files specially tailored to interact with data sources. 3. They are custom built to make the awesome visualizations that Tableau generates.Here you can see a picture of a .twb file opened in Notepad++. 2.What is the Dimensions and Measures? Dimension: A dimension is a field that can be considered an independent variable.Dimensions typically produce headers when added to the rows or columns shelves inthe view. By default, Tableau treats any field containing qualitative, categorical informationas a dimension. This includes, for instance, any field with text or dates values.This means that a measure can be aggregated for each value of the dimension. For instance, you might calculate the Sum of “Sales” for every “State”. In this case the Statefield is acting as a dimension because you want to aggregate sales for each state. Thevalues of Sales are dependent on the State, so State is an independent field and Sales is a dependent field Measure: A measure is a field that is a dependent variable; that is, its value is a function ofone or more dimensions. Measures typically produce axes when added to the rows or columns shelves. By default, Tableau treats any field containing numeric (quantitative) information as a measure. This means that a measure is a function of other dimensions placed on the worksheet. For instance, you might calculate the Sum of “Sales” for every “State”. In this case, the Sales field is acting as a measure because you want to aggregate the field for each state. But measures could also result in a non-numeric result. For instance, you might create a calculated measure called “Sales Rating” that results in the word “Good” if sales are good and “Bad” otherwise. In this case the “Sales Rating” field acts as a measure even though it produces a non-numeric result. It is considered a measure because it is a function of the dimensions in the view. 3.What is KPI in Tableau.? We can easily create a view that shows Key Progress Indicators (KPIs). To do this, you complete the following tasks: ∑ Create the base view with the fields you want to measure. ∑ Build a calculated field that establishes the figure from which you measure progress for the data you’re measuring. ∑ Use shapes that Tableau provides that are designed specifically for KPIs. This example shows how to build a KPI view that shows a green check mark for any sales figure over $125,000, and a red X for any sales figure under $125,000. 4.Preparing data for Tableau. 1. Cleanup dimensions and measure names. 2. Set attribute aliases. 3. Set default colors 4. Set default measure aggregations. 5. Create calculated fields. 5.Is Parameter have it’s dropdown list..? Yes, But it will be called as Compact list. 6.What is the criteria to blend the data from multiple data sources.? There should be a common dimension to blend the data source into single worksheet. For example, when blending Acutal and Target sales data, the two data sources may have a Date field in common. The Date field must be used on the sheet. Then when you switch to the secondary data source in the Data window, Tableau automatically links fields that have the same name. If they don’t have the same name, you can define a custom relationship that creates the correct mapping between fields. 7.Can we use Groups and Sets in calculation field.? ∑ Groups: No, we can not use Groups in calculation fields. ∑ Sets: Yes, we can use Sets in calculation fields. 8.Difference between Grouping and Sets.? ∑ Groups – Combine dimension members 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. 9.What is context filter in Tableau 7.0? If you are applying filters to a large data source, you can improve performance by setting up context filters. A context filter is applied to the data source first, and then the other filters are applied only to the resulting records. This sequence avoids applying each filter to each record in the data source. You may create a context filter to: ∑ Improve performance – If you set a lot of filters or have a large data source, the queries can be slow. You can set one or more context filters to improve performance. ∑ Create a dependent numerical or top N filter – You can set a context filter to include only the data of interest, and then set a numerical or a top N filter. 10.What is Dual Axis.? You can compare multiple measures using dual axes, which are two independent axes that are layered on top of each other. Dual axes are useful when you have two measures that have different scales. For example, the view below shows Dow Jones and NASDAQ close values over time. To add the measure as dual axis drag the field to the right side of the view and drop it when you see a black dashed line. You can also select Dual Axis on the field menu for the measure. 21.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. 22.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) 23.What kind of technology is a Tableau Viz? It is a thin AJAX based JavaScript application 24.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 bemore space than needed. 25.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 th e 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. 26.Can you explain about table calculations? These are inbuilt calculations in tableau which we normally use to calculate Percentage from or for YTD and other calculations like the measure across table, below table and etc.. 27.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. 28.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. 29.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. 30.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 31.Name the components of dashboard? ∑ Horizontal ∑ Vertical ∑ Text ∑ Images etc 32.Can we have multiple value selection in parameter? No 33.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. 34.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 35.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: 1. 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. 2. 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. 3. 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. 36.What is Tableau Reader? Tableau Reader is a free viewing application that lets anyone read and interact with packaged workbooks created by Tableau Desktop. 37.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. 38.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. 39.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. 40.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. 41.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 result set is small relative to the size of the underlying data, and visualizations focus on aggregation and filtering to identify trends and outliers. The small result sets 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 Disaggregating data refers to viewing each data source row, while analyzing data both independently and dependently. 56.What are the limitations of context filters? Tableau takes time to place a filter in context. When a filter is set as context one, the software creates a temporary table for that particular context filter. This table will reload each time and consists of all values that are not filtered by either Context or Custom SQL filter. 57.Name the file extensions in Tableau. There are a number of file types and extensions in Tableau: • Tableau Workbook (.twb) • Tableau Packaged Workbook (.twbx) • Tableau Datasource (.tds) • Tableau Packaged Datasource (.tdsx) • Tableau Data extract (.tde) • Tableau Bookmark (.tdm) • Tableau Map Source (.tms) • Tableau Preferences (.tps) 58.Explain the difference between .twb and .twbx .twb is the most common file extension used in Tableau, which presents an XML format file and comprises all the information present in each dashboard and sheet like what fields are used in the views, styles and formatting applied to a sheet and dashboard. But this workbook does not contain any data. The Packaged workbook merges the information in a Tableau workbook with the local data available (which is not on server). .twbx serves as a zip file, which will include custom images if any. Packaged Workbook allows users to share their workbook information with other Tableau Desktop users and let them open it in Tableau Reader. 59.What are Extracts and Schedules in Tableau server Data extracts are the first copies or subdivisions of the actual data from original data sources. The workbooks using data extracts instead of those using live DB connections are faster since the extracted data is imported in Tableau Engine. After this extraction of data, users can publish the workbook, which also publishes the extracts in Tableau Server. However, the workbook and extracts won’t refresh unless users apply a scheduled refresh on the extract. Scheduled Refreshes are the scheduling tasks set for data extract refresh so that they get refreshed automatically while publishing a workbook with data extract. This also removes the burden of republishing the workbook every time the concerned data gets updated. 60.Name the components of a Dashboard. • Horizontal • Vertical • Text • Image Extract • Blank page • Web [URL ACTION] 61.How to view underlying SQL Queries in Tableau? Viewing underlying SQL Queries in Tableau provides two options: • Create a Performance Recording to record performance information about the main events you interact with workbook. Users can view the performance metrics in a workbook created by Tableau. Help> Settings and Performance> Start Performance Recording Help> Setting and Performance > Stop Performance Recording• Reviewing the Tableau Desktop Logs located at C:\Users\\My Documents\My Tableau Repository. For live connection to data source, you can check log.txt and tabprotosrv.txt files. For an extract, check tdeserver.txt file. 62.Define Page shelf Tableau provides a distinct and powerful tool to control the output display known as Page shelf. As the name suggests, the page shelf fragments the view into a series of pages , presenting a different view on each page, making it more user-friendly and minimizing scrolling to analyze and view data and information. You can flip through the pages using the specified controls and compare them at a common axle. 63.How to Perform Testing in Tableau? Performance testing is again an important part of implementing Tableau. This can be done by loading Testing Tableau Server with TabJolt, which is a “Point and Run” load generator created to perform QA. While TabJolt is not supported by Tableau directly, it has to be installed using other open source products. 64.Explain the concept of Dual Axis? Dual Axis is an excellent phenomenon supported by Tableau that helps users view two scales of two measures in the same graph. Many websites like Indeed.com and other make use of dual axis to show the comparison between two measures and their growth rate in a septic set of years. Dual axes let you compare multiple measures at once, having two independent axes layered on top of one another. 65.How many maximum tables you can join in Tableau? The maximum number of 32 tables can be joined in Tableau. A table size must also be limited to 255 columns (fields). 66.How to remove ‘All’ options from a Tableau auto-filter? 67.How to add Custom Color to Tableau? 68.What different products Tableau provide? • Tableau Server :on-premise or cloud-hosted software to access the workbooks built • Tableau desktop: desktop environment to create and publish standard and packaged workbooks. • Tableau Public: workbooks available publicly online for users to download and access the included data. • Tableau Reader: get a local access to open Tableau Packaged workbook 69.How can you display top five and last five sales in same view? Create two sets, one for top 5 another for bottom 5 and the join these two sets displaying a unique set of total 10 rows. 70.What is TDE file? TDE is a Tableau desktop file that contains with a .tde extension referring to the file containing data extracted from external sources like MS Excel, MS Access or CSV file. 71.How to use group in calculated field? By adding the same calculation to ‘Group By’ clause in SQL query or creating a Calculated Field in the Data Window and using that field whenever you want to group the fields. 72.Can parameters have dropdown list? Yes, parameters do have their independent dropdown lists enabling users to view the data entries available in the parameter during its creation. ****************