Interview Questions

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1. How can u improve performance of tableau server?

Answer:  Avoid Quick filter as possible. If required, we can use context filter for better performance. Better web browser. Use extracts instead of live connection. Use cache mechanism Use incremental extractions Avoid the high resolutions images Adjust the count of application server and vizql server for hitting cache. Set both at 1x to 2x times the number of processing cores present on the server User should not access the dashboard while loading the data

2. If my dashboard is taking long time to render on server what could be the reason?

Answer: Use Window_sum() instead of totals(). It is slow while extracting. Avoid quick filters in dashboards Source data bins give better performance than tableau bins. Use sql query instead of data blending if you are using RDBMS. Use less than 5 views in dashboard. Optimizing data extracts

3.When 10 worksheets are combined and made a complete dashboard if one worksheet is Is it necessary to publish only changed worksheet or entire dashboard?

Answer:  Only changed worksheet.

4.Which databases gives best performance when connected live?

Answer:  Expected answer from you. Please suggest us. Analytical databases are good for tableau. Means OLAP. Exact Ans: Native databases

5.What if customer is asking for data refreshed at minute level? What would you suggest to the customer?

Answer:  It is performance degrade. Using Java Script APIs we do that.

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

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

7.What is Data Visualization?

Answer:  A much advanced, direct, precise and ordered way of viewing large volumes of data is called data visualization. It is the visual representation of data in the form of graphs and charts, especially when you can’t define it textually. You can show trends, patters and correlations through various data visualization software and tools; Tableau is one such data visualization software used by businesses and corporates.

8.What are the differences between Tableau desktop and Tableau Server?

Answer:  While Tableau desktop performs data visualization and workbook creation, Tableau server is used to distribute these interactive workbooks and/or reports to the right audience. Users can edit and update the workbooks and dashboards online or Server but cannot create new ones. However, there are limited editing options when compared to desktop. Tableau Public is again a free tool consisting of Desktop and Server components accessible to anyone.

9.Define parameters in Tableau and their working.

Answer:  Tableau parameters are dynamic variables/values that replace the constant values in data calculations and filters. For instance, you can create a calculated field value returning true when the score is greater than 80, and otherwise false. Using parameters, one can replace the constant value of 80 and control it dynamically in the formula.

10.Differentiate between parameters and filters in Tableau.

Answer:  The difference actually lies in the application. Parameters allow users to insert their values, which can be integers, float, date, string that can be used in calculations. However, filters receive only values users choose to ‘filter by’ the list, which cannot be used to perform calculations. Users can dynamically change measures and dimensions in parameter but filters do not approve of this feature.

11.What are fact table and Dimension table in Tableau?

Answer:  1. Facts are the numeric metrics or measurable quantities of the data, which can be analyzed by dimension table. Facts are stores in Fact table that contain foreign keys referring uniquely to the associated dimension tables. The fact table supports data storage at atomic level and thus, allows more number of records to be inserted at one time. For instance, a Sales Fact table can have product key, customer key, promotion key, items sold, referring to a specific event. 2. Dimensions are the descriptive attribute values for multiple dimensions of each attribute, defining multiple characteristics. A dimension table ,having reference of a product key form the fact table, can consist of product name, product type, size, colour, description, etc.

12.What are Quick Filters in Tableau?

Answer: Global quick filters are a way to filter each worksheet on a dashboard until each of them contains a dimension. They are very useful for worksheets using the same data source, which sometimes proves to a disadvantage and generate slow results. Thus, parameters are more useful.

13.State limitations of parameters in Tableau.

Answer: Parameters facilitate only four ways to represent data on a dashboard (which are seven in quick filters). Further, parameters do not allow multiple selections in a filter.

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

Answer: 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.

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

Answer: 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.

16.What are the differences between twb and twbx?

Answer:   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 dat Answer:   A twbx is a ‘zipped’ archive containing a twb and any external files such as extracts and background images.

17.What is Aggregation & Disaggregation?

Answer: 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.

18.What are the differences between groups and sets?

 Answer: 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.

 19.How do we do testing in Tableau?

 Answer: 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.

20.What is Pages shelf?

Answer: 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.  

21.Best features of tableau and limitations of tableau.

ANSWER:  Best visualizations with less it cost, can connect to any database, no plug-in required and powerful in memory processing. Limitation : Only supports Windows and Mac. No support to Linux based systems.

22.what are the file size limitations with tableau?

ANSWER:  Officially no limit, but we have observed best performance with 4GB of data and 278 columns.

23.what is the max file size u used in tableau.

 ANSWER:  4GB many max columns we can use in tableau.

ANSWER:  If you source is Access then 255.

24.what are the limitations of tableau based on size, number of calculations,

ANSWER:  No Limitation ,but suggested to work with extracts with max 4 GB.

 25.have u ever used tableau to perform ETL or any complex calculations

ANSWER:  Tableau is a Ajax based Java Scripting data Visualisation tool and it cannot perform any ETL actions, Complex calculation : Using Parameter in calculations.

 26.have u faced any problems with file size and number of columns which we use in tableau

ANSWER:  So far no as i have been working with limited data:

27.what is tableau architecture.

ANSWER:  It is Client and Server based N-Tier Architecture. We build Tableau reports in using Tableau Desktop and Deploy them to Tableau Server. Tableau Server runs on 3 difference services Visual Server: This sends the queries to database and then coverts it to the visuals/Images you see in tableau. Database/Repository Server: This manages the connectivity and maintains the data extracts. Application Server: This handles the Authentication and Authorization.] 

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

Answer: A dashboard is a collection of several worksheets and supporting information shown in a single place so you can compare and monitor a variety of data simultaneously. For example, you may have a set of views that you review every day. Rather than flipping through each worksheet, you can create a dashboard that displays all the views at once. You can create a dashboard in much the same way you create a new worksheet. Select Dashboard > New Dashboard. Alternatively, click the New Dashboard tab along the bottom of the workbook. A new tab for the dashboard is added along the bottom of the workbook. Switch to the new dashboard to add views and objects. When you open a dashboard the Dashboard window replaces the Data window on the left side of the workbook. The Dashboard window lists the worksheets that are currently in the workbook. As you create new worksheets, the Dashboard window updates so you always have all worksheets available when adding to a dashboard it. After a view is added to the dashboard, the worksheet is marked with a check mark in the Dashboard window. Also, any legends or quick filters that are turned on for the sheet are automatically added to the dashboard. By default, dashboards use a Tiled layout, which means that each view and object is arranged into a single layered grid. You can change the layout to Floating to allow views and objects to overlap. See Organizing Dashboards to learn more about these layouts.

29.How can you schedule the Reports in tableau? Explain briefly?

Answer: Schedules when you publish workbooks that connect to extracts you can schedule the extracts to be refreshed automatically. That way you don’t have to republish the workbook every time the underlying data has updated and you can still get the performance of a data extract. For example, let’s say you have a workbook that connects to a large data warehouse that is updated weekly. Instead of publishing a workbook that queries the live data, you can create an extract including just the data necessary. This increases performance and avoids queries to the live database. Then you can add that workbook to a schedule so that the extract is refreshed at regular intervals with updated data from the data warehouse. Schedules are created and managed on the server by an administrator. However, an administrator can allow you to add a workbook to a schedule when you are publishing from Tableau Desktop. 1. As you are publishing a workbook, in the Publish Workbook to Tableau Server dialog box, click Scheduling & Authentication. 2. In the Scheduling & Authentication dialog box, select a schedule for the workbook: All data sources that require authentication must have an embedded password so that the extract can be refreshed. This includes data sources that are not extracts.

30.What is the major difference between 7.0 and 8.0 in tableau? And latest?

Answer:  1. New visualizations are introduced like tree map, bubble chart and box and whisker plot. 2. We can copy worksheet directly from one workbook to another workbook. 3. Introduced R script.