SQL Questions

1. What are the two authentication modes in SQL Server?

There are two authentication modes –

• Windows Mode
• Mixed Mode

Modes can be changed by selecting the tools menu of SQL Server configuration properties and choose security page.

2. What Is SQL Profiler?

SQL Profiler is a tool which allows system administrator to monitor events in the SQL server. This is mainly used to capture and save data about each event of a file or a table for analysis.

3. What is recursive stored procedure?

SQL Server supports recursive stored procedure which calls by itself. Recursive stored procedure can be defined as a method of problem solving wherein the solution is arrived repetitively. It can nest up to 32 levels.

CREATE PROCEDURE [dbo].[Fact]
(
@Number Integer,
@RetVal Integer OUTPUT
)
AS
DECLARE @In Integer
DECLARE @Out Integer
IF @Number != 1
BEGIN
SELECT @In = @Number – 1
EXEC Fact @In, @Out OUTPUT - Same stored procedure has been called again(Recursively)
SELECT @RetVal = @Number * @Out
END
ELSE
BEGIN
SELECT @RetVal = 1
END
RETURN
GO

4. What are the differences between local and global temporary tables?

• Local temporary tables are visible when there is a connection, and are deleted when the connection is closed.

CREATE TABLE #<tablename>

• Global temporary tables are visible to all users, and are deleted when the connection that created it is closed.

CREATE TABLE ##<tablename>

5. What is CHECK constraint?

A CHECK constraint can be applied to a column in a table to limit the values that can be placed in a column. Check constraint is to enforce integrity.

6. Can SQL servers linked to other servers?

SQL server can be connected to any database which has OLE-DB provider to give a link. Example: Oracle has OLE-DB provider which has link to connect with the SQL server group.

7. What is sub query and its properties?

A sub-query is a query which can be nested inside a main query like Select, Update, Insert or Delete statements. This can be used when expression is allowed. Properties of sub query can be defined as

• A sub query should not have order by clause
• A sub query should be placed in the right hand side of the comparison operator of the main query
• A sub query should be enclosed in parenthesis because it needs to be executed first before the main query
• More than one sub query can be included

8. What are the types of sub query?

There are three types of sub query –

• Single row sub query which returns only one row
• Multiple row sub query which returns multiple rows
• Multiple column sub query which returns multiple columns to the main query. With that sub query result, Main query will be executed.

9. What is SQL server agent?

The SQL Server agent plays a vital role in day to day tasks of SQL server administrator(DBA). Server agent's purpose is to implement the tasks easily with the scheduler engine which allows our jobs to run at scheduled date and time.

10. What are scheduled tasks in SQL Server?

Scheduled tasks or jobs are used to automate processes that can be run on a scheduled time at a regular interval. This scheduling of tasks helps to reduce human intervention during night time and feed can be done at a particular time. User can also order the tasks in which it has to be generated.

11. What is COALESCE in SQL Server?

COALESCE is used to return first non-null expression within the arguments. This function is used to return a non-null from more than one column in the arguments.

Example –

Select COALESCE(empno, empname, salary) from employee;

12. How exceptions can be handled in SQL Server Programming?

Exceptions are handled using TRY----CATCH constructs and it is handles by writing scripts inside the TRY block and error handling in the CATCH block.

13. What is the purpose of FLOOR function?

FLOOR function is used to round up a non-integer value to the previous least integer. Example is given

FLOOR(6.7)

Returns 6.

14. Can we check locks in database? If so, how can we do this lock check?

Yes, we can check locks in the database. It can be achieved by using in-built stored procedure called sp_lock.

15. What is the use of SIGN function?

SIGN function is used to determine whether the number specified is Positive, Negative and Zero. This will return +1,-1 or 0.

Example –

SIGN(-35) returns -1

16. What is a Trigger?

Triggers are used to execute a batch of SQL code when insert or update or delete commands are executed against a table. Triggers are automatically triggered or executed when the data is modified. It can be executed automatically on insert, delete and update operations.

17. What are the types of Triggers?

There are four types of triggers and they are:

• Insert
• Delete
• Update
• Instead of

18. What is an IDENTITY column in insert statements?

IDENTITY column is used in table columns to make that column as Auto incremental number or a surrogate key.

19. What is Bulkcopy in SQL?

Bulkcopy is a tool used to copy large amount of data from Tables. This tool is used to load large amount of data in SQL Server.

20. What will be query used to get the list of triggers in a database?

Query to get the list of triggers in database-

Select * from sys.objects where type='tr'

21. What is the difference between UNION and UNION ALL?

• UNION: To select related information from two tables UNION command is used. It is similar to JOIN command.
• UNION All: The UNION ALL command is equal to the UNION command, except that UNION ALL selects all values. It will not remove duplicate rows, instead it will retrieve all rows from all tables.

22. How Global temporary tables are represented and its scope?

Global temporary tables are represented with ## before the table name. Scope will be the outside the session whereas local temporary tables are inside the session. Session ID can be found using @@SPID.

23. What are the differences between Stored Procedure and the dynamic SQL?

Stored Procedure is a set of statements which is stored in a compiled form. Dynamic SQL is a set of statements that dynamically constructed at runtime and it will not be stored in a Database and it simply execute during run time.

24. What is Collation?

Collation is defined to specify the sort order in a table. There are three types of sort order –

1. Case sensitive
2. Case Insensitive
3. Binary

25. How can we get count of the number of records in a table?

Following are the queries can be used to get the count of records in a table -

Select * from <tablename> Select count(*) from <tablename> Select rows from sysindexes where id=OBJECT_ID(tablename) and indid<2

26. What is the command used to get the version of SQL Server?

Select SERVERPROPERTY('productversion')

is used to get the version of SQL Server.

27. What is UPDATE_STATISTICS command?

UPDATE_STATISTICS command is used to update the indexes on the tables when there is a large amount of deletions or modifications or bulk copy occurred in indexes.

28. What is the use of SET NOCOUNT ON/OFF statement?

By default, NOCOUNT is set to OFF and it returns number of records got affected whenever the command is getting executed. If the user doesn't want to display the number of records affected, it can be explicitly set to ON- (SET NOCOUNT ON).

29. Which SQL server table is used to hold the stored procedure scripts?

Sys.SQL_Modules is a SQL Server table used to store the script of stored procedure. Name of the stored procedure is saved in the table called Sys.Procedures.

30. What are Magic Tables in SQL Server?

During DML operations like Insert, Delete, and Update, SQL Server creates magic tables to hold the values during the DML operations. These magic tables are used inside the triggers for data transaction.

31. What is the difference between SUBSTR and CHARINDEX in the SQL Server?

The SUBSTR function is used to return specific portion of string in a given string. But, CHARINDEX function gives character position in a given specified string.

SUBSTRING('Smiley',1,3)

Gives result as Smi

CHARINDEX('i', 'Smiley',1)

Gives 3 as result as I appears in 3rd position of the string

32. How can you create a login?

You can use the following command to create a login

CREATE LOGIN MyLogin WITH PASSWORD = '123';

33. What is ISNULL() operator?

ISNULL function is used to check whether value given is NULL or not NULL in sql server. This function also provides to replace a value with the NULL.

34. What is the use of FOR Clause?

FOR clause is mainly used for XML and browser options. This clause is mainly used to display the query results in XML format or in browser.

35. What will be the maximum number of index per table?

For SQL Server 2008 100 Index can be used as maximum number per table. 1 Clustered Index and 999 Non-clustered indexes per table can be used in SQL Server.

1000 Index can be used as maximum number per table. 1 Clustered Index and 999 Non-clustered indexes per table can be used in SQL Server.

1 Clustered Index and 999 Non-clustered indexes per table can be used in SQL Server.

36. What is the difference between COMMIT and ROLLBACK?

Every statement between BEGIN and COMMIT becomes persistent to database when the COMMIT is executed. Every statement between BEGIN and ROOLBACK are reverted to the state when the ROLLBACK was executed.

37. What is the difference between varchar and nvarchar types?

Varchar and nvarchar are same but the only difference is that nvarhcar can be used to store Unicode characters for multiple languages and it also takes more space when compared with varchar.

38. What is the use of @@SPID?

A @@SPID returns the session ID of the current user process.

39. What is the command used to Recompile the stored procedure at run time?

Stored Procedure can be executed with the help of keyword called RECOMPILE.

Example

Exe <SPName>  WITH RECOMPILE

Or we can include WITHRECOMPILE in the stored procedure itself.

40. How to delete duplicate rows in SQL Server?

Duplicate rows can be deleted using CTE and ROW NUMER feature of SQL Server.

41. Where are SQL Server user names and passwords stored in SQL Server?

User Names and Passwords are stored in sys.server_principals and sys.sql_logins. But passwords are not stored in normal text.

42. What is the difference between GETDATE and SYSDATETIME?

Both are same but GETDATE can give time till milliseconds and SYSDATETIME can give precision till nanoseconds. SYSDATE TIME is more accurate than GETDATE.

43. How data can be copied from one table to another table?

INSERT INTO SELECT

This command is used to insert data into a table which is already created.

SELECT INTO

This command is used to create a new table and its structure and data can be copied from existing table.

44. What is TABLESAMPLE?

TABLESAMPLE is used to extract sample of rows randomly that are all necessary for the application. The sample rows taken are based on the percentage of rows.

45. Which command is used for user defined error messages?

RAISEERROR is the command used to generate and initiates error processing for a given session. Those user defined messages are stored in sys.messages table.

46. What do mean by XML Datatype?

XML data type is used to store XML documents in the SQL Server database. Columns and variables are created and store XML instances in the database.

47. What is CDC?

CDC is abbreviated as Change Data Capture which is used to capture the data that has been changed recently. This feature is present in SQL Server 2008.

48. What is SQL injection?

SQL injection is an attack by malicious users in which malicious code can be inserted into strings that can be passed to an instance of SQL server for parsing and execution. All statements have to checked for vulnerabilities as it executes all syntactically valid queries that it receives.

Even parameters can be manipulated by the skilled and experienced attackers.

49. What are the methods used to protect against SQL injection attack?

Following are the methods used to protect against SQL injection attack:

• Use Parameters for Stored Procedures
• Filtering input parameters
• Use Parameter collection with Dynamic SQL
• In like clause, user escape characters

50. What is Filtered Index?

Filtered Index is used to filter some portion of rows in a table to improve query performance, index maintenance and reduces index storage costs. When the index is created with WHERE clause, then it is called Filtered Index

SSAS

What is SSAS?

SQL Server Analysis service (SSAS) is a multi-dimensional OLAP server as well as an analytics engine that allows you to slice and dice large volumes of data. It is part of Microsoft SQL Server and helps perform analysis using various dimensions. It has 2 variants Multidimensional and Tabular. The full form of SSAS is SQL Server Analysis Service.

Architecture of SSAS

The architectural view of SSAS is based on a three-tier architecture, which consists of

1. RDBMS: The data from different sources like Excel, Database, Text, others can be pulled with the help of ETL tool in to the RDBMS.
2. SSAS : Aggregate data from RDBMS is pushed into SSAS cubes by using analysis services projects. The cubes will create an analysis database, and once the analysis database is ready, it can be used for many purposes.
3. Client: Clients can access data using Dashboards, Scorecards, Portals etc.

History of SSAS

• MSOLAP feature first included in SQL Server 7.0. This technology was later purchased from an Israeli company called Panorama.
• Soon it becomes most used OLAP engines because it was included as a part of SQL Server.
• SSAS was renovated entirely with the release of MS-SQL Server 2005
• This latest version also offers a feature for "subcubes" with the Scope statement. This has increased the functionality of the cubes.
• SSAS 2008R2 and 2012 versions are mainly concerned with query performance and scalability
• In Microsoft excel 2010 came an add-in called PowerPivot which uses a local instance of Analysis service with new XVelocity engine which increases the query performance

Important SAAS Terminology

• Data Source
• Data Source View
• Cube
• Dimension Table
• Dimension
• Level
• Fact Table
• Measure
• Schema

Data Source:

Data Source is a kind of connection string. It establishes a connection between the analysis database and RDBMS.

Data Source View:

Data source view is a logical model of Database

Cube:

A cube is a basic unit of storage. It is a collection of data which has been aggregated to allow queries to return data quickly.

MOLAP:

The MOLAP is made of data cube which contains of measures and dimensions. It includes all the members who may be in a hierarchical relationship.

It is specific set of rule which helps you to determine how certain cells are computed in a sparse cube and measures values rolled up inside that hierarchies.

Dimension Table

• A dimension table contains dimensions of a fact.
• They are joined to fact table using a foreign key.
• Dimension tables are de-normalized tables.
• Dimensions offer characteristics of the facts with the help of their attributes.
• Not offers limit set for a given number of dimensions
• The dimension contains one or more hierarchical relationships.

Dimension:

Dimension offers the context surrounding a business process event. In simple terms, they give who, what, where of a fact. In the Sales business process, for the fact sales number, dimensions would be who customer Names.

• Where – Location
• What – Product Name
• In other words, you can say that a dimension is a window to view the information in the facts.

Level:

Each type of summary which can be retrieved from the single dimension is called label.

Fact Table:

A fact table is the most important table in a dimensional model. A Fact Table contains Measurements/fact and Foreign key to the dimension table. For example, payroll operations.

Measure:

Each fact table contains one or more table which should be analyzed. For example, a book sells information table. It can be a profit or loss for the number of book's sold.

Schema:

The database schema of a database system and its structure described in a formal language. It supports the database management system. The term "schema" means to the organization of data as a blueprint of a manner of which database is constructed.

Type of Models in SSAS

Multi-Dimensional Data Model

The Multi-Dimensional Data Model, which consists of a data cube. It is a group of operations which allows you to query the value of cells by using cube and dimension members as coordinates.

It defines rules which decide the way that measure values are rolled up within hierarchies or how specific values are computed in a sparse cube.

Tabular Modeling

Tabular modeling organizes data into related tables. The table doesn't designate as "dimensions" or "facts" and development time is less with tabular because of all related tables able to serve both roles.

Tabular vs. Multidimensional Model

Parameters	Tabular	Multidimensional
Memory	In memory cache	File-based storage
Structure	Loose structure	Rigid structure
Best feature	Data does not need to move from source	It is best when data is put into a star schema.
Type of Model	Relational model	Dimensional model
	DAX	MDX
Complexity	Simple	Complex
Size	Smaller	Larger

Key Features of SSAS

Essential features of SSAS are :

• It offers backward compatibility on the API level.
• You can use OLEDB for OLAP for the client access API and MDX as a query language.
• SSAS helps you to build MOLAP, HOLAP, and ROLAP architectures
• It allows you to work on client-server mode or offline mode.
• You can use SSAS tool with different wizards and designers.
• Data model creation and management is flexible.
• Customize application from extensive support
• Offers Dynamic structure, Ad hoc Report, Shared metadata, and Security features

SSAS vs. PowerPivot

Parameter	SSAS	PowerPivot
What is	SSAS Multidimensional is "Corporate BI"	Microsoft PowerPivot is a "Self- Service BI
Deployment	Deploy to SSAS	It is deployed to SharePoint
Use for	Visual Studio Project	Excel
Size	Size limited to memory	Capacity limited to 2 GB.
Partition support	Supports Partitioning	No partitions
Query type	DirectQuery and Vertipaq	Allows only Vertipaq Queries
Admin tools	Server Admin tools (e.g., SSMS]	Excel and SharePoint "Admin"
Security	Row-level & dynamic security	Workbook file security

Advantages of SSAS

Pros/benefits of SSAS are:

• Helps you to avoid resource contention with the source system
• It is an ideal tool for numeric analysis.
• SSAS enables the discovery of data patterns that may not be immediately apparent using the data mining features built into the product.
• It offers a unified and integrated view of all your business data Reporting, analysis of Key Performance Indicator (KPI) scorecards Data mining.
• SSAS offers online analytic processing (OLAP) of data from different data sources.
• It allows users to analyze data with a host of tools, including SSRS and Excel.

Disadvantages of using SSAS

• Once you select a path(Tabular or Multidimensional) you cannot migrate to the other version without starting over
• You are not allowed to "merge" data between Tabular and Multidimensional cubes
• Tabular proves to be risky if requirements change mid-way through the project

Best practices of using SSAS

• Optimize Cube And Measure Group Design
• You should define useful Aggregations
• Use Partitions method
• Write Efficient MDX
• Use The Query Engine Cache Efficiently
• Scale Out When You Can No-Longer Scale Up
• 
  

Power BI

1). What are the parts of Microsoft self-service business intelligence solution?

Ans: Microsoft has two parts for Self-Service BI

Parts of Self-Service BI

Excel BI Toolkit	It allows users to create an interactive report by importing data from different sources and model data according to report requirement.
Power BI	It is the online solution that enables you to share the interactive reports and queries that you have created using the Excel BI Toolkit.

2). What is self-service business intelligence?

Ans: Self-Service Business Intelligence (SSBI)

• SSBI is an approach to data analytics that enables business users to filter, segment, and, analyze their data, without the in-depth technical knowledge in statistical analysis, business intelligence (BI).
• SSBI has made it easier for end users to access their data and create various visuals to get better business insights.
• Anybody who has a basic understanding of the data can create reports to build intuitive and shareable dashboards.

3). What is Power BI?

Ans: Power BI is a cloud-based data sharing environment. Once you have developed reports using Power Query, Power Pivot and Power View, you can share your insights with your colleagues. This is where Power BI enters the equation. Power BI, which technically is an aspect of SharePoint online, lets you load Excel workbooks into the cloud and share them with a chosen group of co-workers. Not only that, but your colleagues can interact with your reports to apply filters and slicers to highlight data. They are completed by Power BI, a simple way of sharing your analysis and insights from the Microsoft cloud.

Power BI features allow you to:

• Share presentations and queries with your colleagues.
• Update your Excel file from data sources that can be on-site or in the cloud.
• Display the output on multiple devices. This includes PCs, tablets, and HTML 5-enabled mobile devices that use the Power BI app.
• Query your data using natural language processing (or Q&A, as it is known).

4). What is Power BI Desktop?

Ans: Power BI Desktop is a free desktop application that can be installed right on your own computer. Power BI Desktop works cohesively with the Power BI service by providing advanced data exploration, shaping, modeling, and creating report with highly interactive visualizations. You can save your work to a file or publish your data and reports right to your Power BI site to share with others.

5). What data sources can Power BI connect to?

Ans: The list of data sources for Power BI is extensive, but it can be grouped into the following:

• Files: Data can be imported from Excel (.xlsx, xlxm), Power BI Desktop files (.pbix) and Comma Separated Value (.csv).
• Content Packs: It is a collection of related documents or files that are stored as a group. In Power BI, there are two types of content packs, firstly those from services providers like Google Analytics, Marketo or Salesforce and secondly those created and shared by other users in your organization.
• Connectors to databases and other datasets such as Azure SQL, Databaseand SQL, Server Analysis Services tabular data, etc.

6). What are Building Blocks in Power BI?

Ans: The following are the Building Blocks (or) key components of Power BI:

1. Visualizations: Visualization is a visual representation of data.
   Example: Pie Chart, Line Graph, Side by Side Bar Charts, Graphical Presentation of the source data on top of Geographical Map, Tree Map, etc.
2. Datasets: Dataset is a collection of data that Power BI uses to create its visualizations.
   Example: Excel sheets, Oracle or SQL server tables.
3. Reports: Report is a collection of visualizations that appear together on one or more pages.
   Example: Sales by Country, State, City Report, Logistic Performance report, Profit by Products report etc.
4. Dashboards: Dashboard is single layer presentation of multiple visualizations, i.e we can integrate one or more visualizations into one page layer.
   Example: Sales dashboard can have pie charts, geographical maps and bar charts.
5. Tiles: Tile is a single visualization in a report or on a dashboard.
   Example: Pie Chart in Dashboard or Report.

7). What are the different types of filters in Power BI Reports?

Ans: Power BI provides variety of option to filter report, data and visualization. The following are the list of Filter types.

• Visual-level Filters: These filters work on only an individual visualization, reducing the amount of data that the visualization can see. Moreover, visual-level filters can filter both data and calculations.
• Page-level Filters: These filters work at the report-page level. Different pages in the same report can have different page-level filters.
• Report-level Filters: There filters work on the entire report, filtering all pages and visualizations included in the report.

We know that Power BI visual have interactions feature, which makes filtering a report a breeze. Visual interactions are useful, but they come with some limitations:

• The filter is not saved as part of the report. Whenever you open a report, you can begin to play with visual filters but there is no way to store the filter in the saved report.
• The filter is always visible. Sometimes you want a filter for the entire report, but you do not want any visual indication of the filter being applied.

8). What are content packs in Power BI?

Ans: Content packs for services are pre-built solutions for popular services as part of the Power BI experience. A subscriber to a supported service, can quickly connect to their account from Power BI to see their data through live dashboards and interactive reports that have been pre-built for them. Microsoft has released content packs for popular services such as Salesforce.com, Marketo, Adobe Analytics, Azure Mobile Engagement, CircuitID, comScore Digital Analytix, Quickbooks Online, SQL Sentry and tyGraph. 

Organizational content packs provide users, BI professionals, and system integrator the tools to build their own content packs to share purpose-built dashboards, reports, and datasets within their organization.

Power BI Interview Questions – DAX

9). What is DAX?

Ans: To do basic calculation and data analysis on data in power pivot, we use Data Analysis Expression (DAX). It is formula language used to compute calculated column and calculated field.

• DAX works on column values.
• DAX can not modify or insert data.
• We can create calculated column and measures with DAX  but we can not calculate rows using DAX.

Sample DAX formula syntax:

For the measure named Total Sales, calculate (=) the SUM of values in the [SalesAmount] column in the Sales table.

A- Measure Name
B- = – indicate beginning of formula
C- DAX Function
D- Parenthesis for Sum Function
E- Referenced Table
F- Referenced column name

10). What are the most common DAX Functions used?

Ans: Below are some of the most commonly used DAX function: 

• SUM, MIN, MAX, AVG, COUNTROWS, DISTINCTCOUNT
• IF, AND, OR, SWITCH
• ISBLANK, ISFILTERED, ISCROSSFILTERED
• VALUES, ALL, FILTER, CALCULATE,
• UNION, INTERSECT, EXCEPT, NATURALINNERJOIN, NATURALLEFTEROUTERJOIN,
  SUMMARIZECOLUMNS, ISEMPTY,
• VAR (Variables)
• GEOMEAN, MEDIAN, DATEDIFF

11). How is the FILTER function used?

Ans: The FILTER function returns a table with a filter condition applied for each of its source table rows. The FILTER function is rarely used in isolation, it’s generally used as a parameter to other functions such as CALCULATE. 

• FILTER is an iterator and thus can negatively impact performance over large source tables.
• Complex filtering logic can be applied such as referencing a measure in a filter expression.
  • FILTER(MyTable,[SalesMetric] > 500)

12). What is special or unique about the CALCULATE and CALCULATETABLE functions?

Ans: These are the only functions that allow you modify filter context of measures or tables.

• Add to existing filter context of queries.
• Override filter context from queries.
• Remove existing filter context from queries.

Limitations:

• Filter parameters can only operate on a single column at a time.
• Filter parameters cannot reference a metric.

13). What is the common table function for grouping data?

Ans:  SUMMARIZE()

• Main groupby function in SSAS.
• Recommended practice is to specify table and group by columns but not metrics.You can use ADDCOLUMNS function.

 SUMMARIZECOLUMNS

• New group by function for SSAS and Power BI Desktop; more efficient.
• Specify group by columns, table, and expressions.

14). What are some benefits of using Variables in DAX ?

Ans: Below are some of the benefits: 

• By declaring and evaluating a variable, the variable can be reused multiple times in a DAX expression, thus avoiding additional queries of the source database.
• Variables can make DAX expressions more intuitive/logical to interpret.
• Variables are only scoped to their measure or query, they cannot be shared among measures, queries or be defined at the model level.

15). How would you create trailing X month metrics via DAX against a non-standard calendar?

Ans:  The  solution will involve:

1. CALCULATE function to control (take over) filter context of measures.
2. ALL to remove existing filters on the date dimension.
3. FILTER to identify which rows of the date dimension to use.

Alternatively, CONTAINS may be used:

• CALCULATE(FILTER(ALL(‘DATE’),…….))

16). What are the different Excel BI add-in?

Ans: Below are the most important BI add-in to Excel:

• Power Query: It helps in finding, editing and loading external data.
• Power Pivot: Its mainly used for data modeling and analysis.

• Power View: It is used to design visual and interactively reports.
• Power Map: It helps to display insights on 3D Map.

Power BI Interview Questions – Power Pivot

17). What is Power Pivot?

Ans: Power Pivot is an add-in for Microsoft Excel 2010 that enables you to import millions of rows of data from multiple data sources into a single Excel workbook. It lets you create relationships between heterogeneous data, create calculated columns and measures using formulas, build PivotTables and PivotCharts. You can then further analyze the data so that you can make timely business decisions without requiring IT assistance.

18). What is Power Pivot Data Model?

Ans: It is a model that is made up of data types, tables, columns, and table relations. These data tables are typically constructed for holding data for a business entity.

19). What is xVelocity in-memory analytics engine used in Power Pivot?

Ans: The main engine behind power pivot is the xVelocity in-memory analytics engine. It can handle large amount of data because it stores data in columnar databases, and in memory analytics which results in faster processing of data as it loads all data to RAM memory.

21). What are some of differences in data modeling between Power BI Desktop and Power Pivot for Excel?

Ans: Here are some of the differences:

• Power BI Desktop supports bi-directional cross filtering relationships, security, calculated tables, and Direct Query options.
• Power Pivot for Excel has single direction (one to many) relationships, calculated columns only, and supports import mode only. Security roles cannot be defined in Power Pivot for Excel.

22). Can we have more than one active relationship between two tables in data model of power pivot?

Ans: No, we cannot have more than one active relationship between two tables. However, can have more than one relationship between two tables but there will be only one active relationship and many inactive relationship. The dotted lines are inactive and continuous line are active.

Power BI Interview Questions – Power Query

23). What is Power Query?

Ans: Power query is a ETL Tool used to shape, clean and transform data using intuitive interfaces without having to use coding. It helps the user to:

• Import Data from wide range of sources from files, databases, big data, social media data, etc.
• Join and append data from multiple data sources. 
  • Shape data as per requirement by removing and adding data.

24). What are the data destinations for Power Queries?

Ans: There are two destinations for output we get from power query:

1. Load to a table in a worksheet.
2. Load to the Excel Data Model.

25). What is query folding in Power Query?

Ans: Query folding is when steps defined in Power Query/Query Editor are translated into SQL and executed by the source database rather than the client machine. It’s important for processing performance and scalability, given limited resources on the client machine.

26). What are some common Power Query/Editor Transforms?

Ans: Changing Data Types, Filtering Rows, Choosing/Removing Columns, Grouping, Splitting a column into multiple columns, Adding new Columns ,etc.

27). Can SQL and Power Query/Query Editor be used together?

Ans: Yes, a SQL statement can be defined as the source of a Power Query/M function for additional processing/logic. This would be a good practice to ensure that an efficient database query is passed to the source and avoid unnecessary processing and complexity
by the client machine and M function.

28). What are query parameters and Power BI templates?

Ans:Query parameters can be used to provide users of a local Power BI Desktop report with a prompt, to specify the values they’re interested in.

• The parameter selection can then be used by the query and calculations.
• PBIX files can be exported as Templates (PBIT files).
• Templates contain everything in the PBIX except the data itself.

Parameters and templates can make it possible to share/email smaller template files and limit the amount of data loaded into the local PBIX files, improving processing time and experience .

29). Which language is used in Power Query?

Ans: A new programming language is used in power query called M-Code. It is easy to use and similar to other languages. M-code is case sensitive language.

30). Why do we need Power Query when Power Pivot can import data from mostly used sources?

Ans: Power Query is a self-service ETL (Extract, Transform, Load) tool which runs as an Excel add-in. It allows users to pull data from various sources, manipulate said data into a form that suits their needs and load it into Excel. It is most optimum to use Power Query over Power Pivot as it lets you not only load the data but also manipulate it as per the users needs while loading.

Power BI Interview Questions – Power Map

31). What is Power Map?

Ans: Power Map is an Excel add-in that provides you with a powerful set of tools to help you visualize and gain insight into large sets of data that have a geo-coded component. It can help you produce 3D visualizations by plotting upto a million data points in the form of column, heat, and bubble maps on top of a Bing map. If the data is time stamped, it can also produce interactive views that display, how the data changes over space and time.

32). What are the primary requirement for a table to be used in Power Map?

Ans: For a data to be consumed in power map there should be location data like:

• Latitude/Longitude pair
• Street, City, Country/Region, Zip Code/Postal Code, and State/Province, which can be geolocated by Bing

The primary requirement for the table is that it contains unique rows. It must also contain location data, which can be in the form of a Latitude/Longitude pair, although this is not a requirement. You can use address fields instead, such as Street, City, Country/Region, Zip Code/Postal Code, and State/Province, which can be geolocated by Bing.

33). What are the data sources for Power Map?

Ans: The data can either be present in Excel or could be present externally. To prepare your data, make sure all of the data is in Excel table format, where each row represents a unique record. Your column headings or row headings should contain text instead of actual data, so that Power Map will interpret it correctly when it plots the geographic coordinates. Using meaningful labels also makes value and category fields available to you when you design your tour in the Power Map Tour Editor pane.

To use a table structure which more accurately represents time and geography inside Power Map, include all of the data in the table rows and use descriptive text labels in the column headings, like this:

In case you wish to load your data from an external source:

1. In Excel, click Data > the connection you want in the Get External Data group.
2. Follow the steps in the wizard that starts.
3. On the last step of the wizard, make sure Add this data to the Data Model is checked.

Power BI Interview Questions – Additional Questions

34). What is Power View?

Ans: Power View is a data visualization technology that lets you create interactive charts, graphs, maps, and other visuals which bring your data to life. Power View is available in Excel, SharePoint, SQL Server, and Power BI.

The following pages provide details about different visualizations available in Power View:

• Charts 
• Line charts 
• Pie charts 
• Maps
• Tiles 
• Cards 
• Images
• Tables
• Power View
• Multiples Visualizations 
• Bubble and scatter charts 
• Key performance indicators (KPIs) 

35). What is Power BI Designer?

Ans: It is a stand alone application where we can make Power BI reports and then upload it to Powerbi.com, it does not require Excel. Actually, it is a combination of Power Query, Power Pivot, and Power View.

36). Can we refresh our Power BI reports once uploaded to cloud (Share point or Powebi.com)?

Ans: Yes we can refresh our reports through Data Management gateway(for sharepoint), and Power BI Personal gateway(for Powerbi.com)

37). What are the different types of refreshing data for our published reports?

Ans: There are four main types of refresh in Power BI. Package refresh, model or data refresh, tile refresh and visual container refresh.

• Package refresh

This synchronizes your Power BI Desktop, or Excel, file between the Power BI service and OneDrive, or SharePoint Online. However, this does not pull data from the original data source. The dataset in Power BI will only be updated with what is in the file within OneDrive, or SharePoint Online.

• Model/data refresh

It referrs to refreshing the dataset, within the Power BI service, with data from the original data source. This is done by either using scheduled refresh, or refresh now. This requires a gateway for on-premises data sources.

• Tile refresh

Tile refresh updates the cache for tile visuals, on the dashboard, once data changes. This happens about every fifteen minutes. You can also force a tile refresh by selecting the ellipsis (…) in the upper right of a dashboard and selecting Refresh dashboard tiles.

• Visual container refresh

Refreshing the visual container updates the cached report visuals, within a report, once the data changes.

To know more about data refresh and understand how to implement data refresh, you can check the following link.

38). Is Power BI available on-premises?

Ans: No, Power BI is not available as a private, internal cloud service. However, with Power BI and Power BI Desktop, you can securely connect to your own on-premises data sources. With the On-premises Data Gateway, you can connect live to your on-premises SQL Server Analysis Services, and other data sources. You can also scheduled refresh with a centralized gateway. If a gateway is not available, you can refresh data from on-premises data sources using the Power BI Gateway – Personal.

39). What is data management gateway and Power BI personal gateway?

Ans: Gateway acts a bridge between on-premises data sources and Azure cloud services.

Personal Gateway:

• Import Only, Power BI Service Only, No central monitoring/managing.
• Can only be used by one person (personal); can’t allow others to use this gateway.

On-Premises Gateway:

• Import and Direct Query supported.
• Multiple users of the gateway for developing content.
• Central monitoring and control.

40). What is Power BI Q&A?

Ans: Power BI Q&A is a natural language tool which helps in querying your data and get the results you need from it. You do this by typing into a dialog box on your Dashboard, which the engine instantaneously generates an answer similar to Power View. Q&A interprets your questions and shows you a restated query of what it is looking from your data. Q&A was developed by Server and Tools, Microsoft Research and the Bing teams to give you  a complete feeling of truly exploring your data.

41). What are some ways that Excel  experience can be leveraged with Power BI?

Ans: Below are some of the ways through which we can leverage Power BI:

• The Power BI Publisher for Excel:
  • Can be used to pin Excel items (charts, ranges, pivot tables) to Power BI Service.
  • Can be used to connect to datasets and reports stored in Power BI Service.
• Excel workbooks can be uploaded to Power BI and viewed in the browser like Excel Services.
• Excel reports in the Power BI service can be shared via Content Packs like other reports.
• Excel workbooks (model and tables) can be exported to service for PBI report creation.
• Excel workbook Power Pivot models can be imported to Power BI Desktop models.

42). What is a calculated column in Power BI and why would you use them?

Ans: Calculated Columns are DAX expressions that are computed during the model’s processing/refresh process for each row of the given column and can be used like any other column in the model.

Calculated columns are not compressed and thus consume more memory and result in reduced query performance. They can also reduce processing/refresh performance if applied on large fact tables and can make a model more difficult to maintain/support given
that the calculated column is not present in the source system.

43). How is data security implemented in Power BI ?

Ans:  Power BI can apply Row Level Security roles to models.

• A DAX expression is applied on a table filtering its rows at query time.
• Dynamic security involves the use of USERNAME functions in security role definitions.
• Typically a table is created in the model that relates users to specific dimensions and a role.

44). What are many-to-many relationships and how can they be addressed in Power BI ?

Ans: Many to Many relationships involve a bridge or junction table reflecting the combinations of two dimensions (e.g. doctors and patients). Either all possible combinations or those combinations that have occurred.

• Bi-Directional Crossfiltering relationships can be used in PBIX.
• CROSSFILTER function can be used in Power Pivot for Excel.
• DAX can be used per metric to check and optionally modify the filter context.

45). Why might you have a table in the model without any relationships to other tables?

Ans: There are mainly 2 reasons why we would have tables without relations in our model:

• A disconnected table might be used to present the user with parameter values to be exposed and selected in slicers (e.g. growth assumption.)
  • DAX metrics could retrieve this selection and use it with other calculations/metrics.
• A disconnected table may also be used as a placeholder for metrics in the user interface.
  • It may not contain any rows of data and its columns could be hidden but all metrics are visible.

46). What is the Power BI Publisher for Excel?

Ans:  You can use Power BI publisher for Excel to pin ranges, pivot tables and charts to Power BI.

• The user can manage the tiles – refresh them, remove them, in Excel.
• Pinned items must be removed from the dashboard in the service (removing in Excel only deletes the connection).
• The Power BI Publisher for Excel can also be used to connect from Excel to datasets that are hosted in the Power BI Service.
• An Excel pivot table is generated with a connection (ODC file) to the data in Azure.

The Publisher installs all necessary drivers on local machine to establish connectivity .

47). What are the differences between a Power BI Dataset, a Report, and a Dashboard?

Ans:  Dataset: The source used to create reports and visuals/tiles.

• A data model (local to PBIX or XLSX) or model in an Analysis Services Server
• Data could be inside of model (imported) or a Direct Query connection to a source.

Report: An individual Power BI Desktop file (PBIX) containing one or more report pages.

• Built for deep, interactive analysis experience for a given dataset (filters, formatting).
• Each Report is connected to atleast one dataset 
• Each page containing one or more visuals or tiles.

Dashboard: a collection of visuals or tiles from different reports and, optionally, a pinned.

• Built to aggregate primary visuals and metrics from multiple datasets.

48) What are the three Edit Interactions options of a visual tile in Power BI Desktop? 

Ans: The 3 edit interaction options are  Filter, Highlight, and None.

Filter: It completely filter a visual/tile based on the filter selection of another visual/tile.

Highlight: It highlight only the related elements on the visual/tile, gray out the non-related items.

None: It ignore the filter selection from another tile/visual.

49). What are some of the differences in report authoring capabilities between using a live or direct query connection such as to an Analysis Services model, relative to working with a data model local to the Power BI Desktop file?

Ans: With a data model local to the PBIX file (or Power Pivot workbook), the author has full control over the queries, the modeling/relationships, the metadata and the metrics.

With a live connection to an Analysis Services database (cube) the user cannot create new metrics, import new data, change the formatting of the metrics, etc – the user can only use the visualization, analytics, and formatting available on the report canvas.

With a direct query model in Power BI to SQL Server, for example, the author has access to the same features (and limitations) available to SSAS  Direct Query mode.

• Only one data source (one database on one server) may be used, certain DAX functions are not optimized, and the user cannot use Query Editor functions that cannot be translated into SQL statements.

50). How does SSRS integrate with Power BI?

Ans: Below are some of the way through which SSRS can be integrated with Power BI: 

• Certain SSRS Report items such as charts can be pinned to Power BI dashboards.
• Clicking the tile in Power BI dashboards will bring the user to the SSRS report.
• A subscription is created to keep the dashboard tile refreshed.
• Power BI reports will soon be able to be published to SSRS portal