QlikView Interview Questions

QlikView has many features that help you quickly create advanced reports from multiple data sources. Below are some of the features that make QlikView unique:

• Natural analytics and data discovery: QlikView searches through all the data stored in the memory in a natural manner. Natural search means that the data searching process does not follow predefined patterns, but instead will search for data and associations in a way that is the most natural. Within QlikView apps, users can quickly discover and analyze data.
• Data collaboration and connectivity: Qlik DataMarket (DaaS) is a unique QlikView cloud-based data service that allows users to fetch data sets from different syndicated and public data sources. Several public datasets are available, including population, currencies, business demographics, weather conditions, economic indicators, etc. RESTful API connectors can also be used to connect and integrate with data sources like Facebook, Alfresco, Twitter, LinkedIn, Adobe, Documentum, etc.
• Data association is automatically maintained: QlikView recognizes or identifies the relationship between every piece of data in a dataset automatically. Therefore, users do not have to pre-configure relationships between data entities.
• In-memory storage capability: In-memory storage technology is one of QlikView's key strengths. Data from different sources (including traditional sources like data warehouses) are loaded or stored into RAM on the system and can later be retrieved directly from there.
• Associative model: QlikView is the only tool that offers an associative data discovery model. It simplifies the process of discovering and analyzing data in BI tools. As a result of these associations, we create a logical connection by linking related data fields and data values with each other.
• Comparative Analysis: Comparative analysis in QlikView is an extension of the associative model. Comparisons of different fields and data sets are possible through comparative analysis. Users and developers can choose which data sections or states to compare. The comparison of data is aided by charts, tables, and graphs for better understanding and analysis.

From the Tools menu, we can choose the Edit menu to edit the tools, and create different kinds of charts with wizards such as the Time Chart Wizard, Quick Chart Wizard, Box Plot Wizard, and Statistics Chart Wizard. Alerts and themes can also be managed using this tool menu.

You can directly enter the data into a QlikView document by typing it in or pasting it in. This is known as inline data. Data can be loaded into QlikView quickly via the clipboard. You can access this feature from the Insert tab of the script editor. As shown below, open up the script editor, and then go to and click on Insert –> Load Statement –> Load Inline option.

As soon as we open the screen above, we see a spreadsheet-like document as shown below where values can be typed. The column headers are generated automatically.

Yes, you can load web files into QlikView using the Script Editor. For connecting to and retrieving data from different data sources, QlikView uses load scripts, which can be managed within the script editor.  The file is loaded into QlikView via the load script, which can be seen in the below screenshot. So, if we use a delimited file, we can tweak/modify the below-given script as required.

QlikView delimited files are text files in which the data fields are separated using commas, semicolons, tabs, etc. These types of files are also known as CSVs (comma-separated values) and have the extension '.csv'. CSV files can be loaded in QlikView. They are useful since they allow storing large amounts of data in a simple text format.

In QlikView, there are several types of QlikView data files available from which data can be loaded. Listed below are a few of them:

• Delimited Files: Store large amounts of data in a simple text format.
• Fixed Record Files: Consist of data records or rows that have the same length or byte size.
• Dif Files (Data Interchange Format files): Used for importing and exporting spreadsheet data. They only contain data from one spreadsheet. 
• Excel (XLS) Files: Contain data created in MS Excel documents.
• Excel (XLSX) Files: Use for storing data from MS Excel documents.
• HTML (HyperText Markup Language) Files: Also known as web files, and contains information on a web page.
• QVD (QlikView Data) Files: A file that can be used to read and write data to and from QlikView. Files like these are mainly used by QlikView services as storage and as intermediate files.
• KML Files (Keyhole Markup Language): A file format for defining and storing geographic data used in earth browsers.

A Qlik macro is generally a set of tasks that you want to automate - for reporting purposes, these tasks would otherwise need to be done manually. This concept is similar to Excel macros. Macros can be used for the following things:

• To reload an application.
• As well as to create objects.

A fact constellation schema is basically a way to represent a multidimensional model. This model includes several fact tables which share some common dimension tables. It can be considered a collection of multiple star schemas and is therefore also known as a galaxy schema.

In the above diagram, yellow-coloured Dimension tables are the ones common to both star schemas. The blue-coloured fact tables correspond to their respective star schemas.

In QlikView, you can bundle or aggregate data from rows within a table by using the Aggregate function. This function lets you apply mathematical or statistical operations on large data chunks collectively. There are different types of aggregate functions in QlikView, each based on the actions they take on the data as shown below: 

A previous() function finds or determines the value of the ‘expr’ expression utilizing the data from the previous input record that hasn't been discarded due to a where clause. The function will return NULL in the first row of an internal table.

Syntax: Previous(expr)

Here, expr is the expression that contains the data to be measured.

QlikView Dashboards are essentially sheets or documents that contain various sheet objects containing the loaded data in the QlikView script. In a dashboard, values from various fields are displayed simultaneously. A dashboard allows users to view and analyze data in several ways and with different types of sheet objects.

In QlikView, there is an object called CONTAINER that allows multiple chart objects to be displayed at once that can be accessed through tabs. In the container, multiple charts are housed in the same box, as shown below. You will see all charts in the same window, but only one will be active at a time, and you can navigate between charts using the bottom tabs. Tab positions can be changed to top, left, or right as well.

Example: Look at the following snapshot. There are four different charts in one container, including Region-wise sales, Manpower distribution, Region-wise profit, and YoY growth. These charts can be accessed by clicking on their respective tabs.

Using the ApplyMap() script function, you can map an expression's output to a previously loaded mapping table.

Syntax:

ApplyMap('map_name', expression [ , default_mapping ] )

Here,  

• map_name: Name of a mapping table that has been created by a load or a select statement.
• expression: The expression refers to the piece of the quote or the condition, whose result should be mapped.
• default_mapping: If the mapping table does not contain a matching value for an expression, this value is used as the default mapping value.

In QlikView, you can use the Mapping Load statement to load data fields and values (from pre-existing tables from various sources and models) into a newly created mapping table. These are temporary tables as they are automatically removed from the data model at the end of the script execution.

Syntax:

Mapping (loadstatement | selectstatement)

Here, the prefix 'Mapping' is used to LOAD/SELECT statements that instruct or command the system to save the loaded fields in a mapping table.

There are different methods or ways to load data into QlikView. Listed below are a few of them:

• Data loading from file: It is a normal method used to load data into the Qlikview application.  Data can be loaded from different types of files, including Excel, CSV, Text files, etc. You can achieve this by creating ODBC (Open Database Connectivity) and OLEDB (Object Linking and Embedding Database) as well as connecting directly to your database.
• Inline load: An inline load is another way to load data, which allows the user to define their own data and load it within Qlikview. It is possible to define Inline Data in the Inline Data Wizard.
• Incremental load: Incremental load in QlikView is used to load only newly added or changed records instead of the entire dataset every day. It will come in handy when a database is large.
• Buffer load: Buffer load in QlikView helps to create and maintain the QVD (QlikView Data) files automatically. 

QlikView and Qlik Sense are the main products offered by the Qlik software company. Both QlikView and Qlik Sense are BI tools and have many similarities, but each is tailored to a particular market and serves a different purpose.

• QlikView Server: Basically, QlikView Server makes QlikView documents available to connected clients. In addition to nesting multiple servers for data load balancing, the QlikView Server enables users to access data both on a PC and on their mobile phones.
• QlikView Publisher: QlikView Publisher handles data management, data access, data reduction, and distribution. In addition to ensuring that the right information reaches the right user at the right time, QlikView Publisher facilitates centralized administration and management. 

The differences between the keep and join commands are as follows:

• QVD: QVD stands for Qlikview data. In the QVD data file, raw data is stored so that it can be later used for the Data Model. Data is stored in compressed form. 
• QVW: QVW stands for Qlikview application. A QVW file contains objects, charts, reports, and a data model. It is used to display data in charts and reports.

The composite key relationship occurs when two or more internal tables have some fields in common. To handle this, QlikView automatically creates synthetic keys. Synthetic keys are fields that represent all possible combinations of composite keys.

Synthetic keys are often indicative of an incorrect data model, but that is not always the case. If, however, you have synthetic keys that are based on other synthetic keys, this is a sure indication that your data model is incorrect.

1. Match(): It compares the first parameter to all the following parameters and returns the total number of expressions that match. It is case-sensitive.

Syntax:

match( str, expr1 [ , expr2,...exprN ])

Example:

match( M, 'Apr','May','Jun')

Here, 
If M=Apr, it will return 1.

If M=Jang, it will return 0.

2. Pick(): This is a QlikView script function. Pick() works the same way as Excel's INDEX() function. It returns the nth expression in the list.

Syntax: 

pick(n, expr1[ , expr2,...exprN])

Example:

pick( N, 'A','B',4, 6 )

Here, 

If N = 2, it will return 'B'.

If N = 3, it will return 4.

• Information Density: It shows the percentage of rows containing a distinct value for a particular field.
• Subset Ratio: It is a measure of the percentage of each distinct value of a particular field in the table as compared to all distinct values of the same field in the entire data model.

Both Kurtosis() and Skew() are types of statistical aggregate functions.

Kurtosis(): This function measures the peak of a distribution curve. A leptokurtic distribution (Kurtosis > 3) has a tall and thin curve. A leptokurtic distribution has values close to the mean or at its extrema. Platykurtic distributions (Kurtosis < 3) have moderately spread out values. Mesokurtic (Kurtosis=3) distributions are defined as distributions whose shape lies between the leptokurtic distribution and the platykurtic distribution.

Skew(): This function measures the asymmetry of a distribution curve. A zero value of skewness causes the distribution curve to split into two equal halves at the median. Negative values of the skewness cause the distribution to have a longer tail towards the left side of the curve. Positive values of the skewness cause the distribution to have a longer tail towards the right side of the curve.

Among Qlikview's unique features are IntervalMatch and Match Functions. Both of those functions are extremely helpful in industrial setups or anywhere where data records change frequently.

• Match(): QlikView's Match Function lets you match a string value expression to the associated data in the table columns. By applying the match function and mentioning the expression you are looking for, you will get the entire data in the table related to that expression.
• IntervalMatch(): QlikView offers the IntervalMatch function as a way of matching numeric values in one table with intervals or durations in another table. The numerical values may be data, timestamps, scores, etc. 

• List Box: Using a list box, you can choose a single field from a table that has been loaded into QlikView memory. As a result, you will see a single list of values for the field you have selected.  When a value is selected in the list box, the related values in the other sheet objects are highlighted. There is also a search feature, which allows you to find specific values within a list box. This is very useful when you have a very long list of values.
• Multi-Box: This type of box displays all the values from multiple fields as drop-down values. This is a compressed table box that displays only the field names in the columns and allows you to view all values of a particular field by using a drop-down menu. This box allows you to save a lot of space on your dashboard or sheet while adding more objects to the dashboard for better analytics. When a value is selected in the list box, the related values in the other sheet objects are highlighted. This speeds up visually analyzing a sheet. Additionally, you can follow drill-down paths among various sheet objects.

The join command in QlikView makes it possible to combine data from two separate data sets into a single set. A join in QlikView is similar to a join in SQL. When the output is generated, only columns and rows whose values match the join conditions are displayed. There are three types of joins as follows:

• Inner Join: With this join, only the rows present in both tables (left and right) are merged and displayed as a single table.
• Outer Join: With this join, all the rows present in both tables (left and right) are merged into and displayed as a single table.
• Left Join: This involves retrieving all the rows from the left table and only the rows matching from the right table.
• Right Join: This involves retrieving all the rows from the right table and only the rows matching from the left table.

To access or open a QlikView document from a QlikView Server (QVS), each client/user requires its own license. A Client Access License (CAL) enables access to QlikView documents residing on a QlikView Server. For CALs, you need a QlikView Publisher license. The following types of CALs are available in QlikView:

• Named User CAL: With Named User CAL, a single named user can have access to all QlikView documents on the QlikView Server for as long as required. Named user CALs are specific to the machine or the user. While this license cannot be shared, it allows users to access any number of documents for an unlimited amount of time.
• Document CAL: With Document CAL, a single named user can access only a single QlikView document on the QlikView Server at any time. A single user can be assigned multiple Document CALs. 
• Session CAL: In a scenario where there are a great number of non-frequent users, session CALs are used. With the Session CAL, a single named or anonymous user has access to all the QlikView documents on the QlikView server. Sessions CALs comprise a pool of licenses that are assigned automatically to users or clients based on the first-come, first-served.
• Usage CAL: With the Usage CAL, a single named or anonymous user has access to a single QlikView document on the QlikView server for 60 minutes every 28 days. Usage CALs comprise a pool of licenses that are assigned automatically to users or clients based on the first-come, first-served.

When a QlikView Server is run with a QVP (QlikView Publisher) license, the following services are available:

• QMS (QlikView Management Service)
• QVWS QlikView (Web Server) 
• QVS (QlikView Server)
• Qlik License Service
• DSC (QlikView Directory Service Connector)
• QDS (QlikView Distribution Service)

When QlikView Server is run without a QVP (QlikView Publisher) license, the following services are available:

• QMS (QlikView Management Service)
• QVWS QlikView (Web Server) 
• QVS (QlikView Server)
• Qlik License Service
• QlikView ReloadEngine (not a service)
• DSC (QlikView Directory Service Connector)

• Tasks: Tasks are used to perform a range of different operations, and they are handled by the QSS (Qlik Sense Scheduler Service). Tasks are generally created for reloading data and distributing dashboards to users.
• Triggers: A task is executed by a trigger or manually from the task overview page.  Triggers are used to schedule a task to be performed at a specific time. Additional triggers can be created to execute the task.

Tables are the most common way of presenting data. Tables in QlikView can be categorized into four types: pivot tables, crosstables, straight tables, and mapping tables. All of these types of QlikView tables display data uniquely.

• Pivot table: Table pivots are commonly used to show the sum of values across several dimensions in a table. It can be used in data analysis. You can create pivot tables using chart objects.
• Straight table: Straight tables are the most basic form of data representation in QlikView. Simple yet powerful, these tables allow you to rearrange columns, sort them, and colour the background.
• Crosstable: Cross tables are tables where the columns and rows swap or switch places. The row’s values repeat themselves for every column value in a cross table. You can create a cross table in the File Wizard.
• Mapping table: This table maps the column values of two tables. Alternatively, it is referred to as a lookup table, which is only used to locate a related value in another table. A mapping table is temporarily created in memory and is automatically dropped after script execution is complete.

There are various types of charts available in QlikView. Some of them are as follows:

• Bar chart: It shows numerical data values as blocks of varying sizes. Bar charts display categories on the x-axis and the corresponding calculated values on the y-axis, such as sums, counts, and averages.
• Line chart: Line charts connect numerical values to present information. A line chart presents information using a series of data points with a continuous line.
• Combo chart: This type of chart combines bar charts and line charts. There will be two measures displayed in a category, one by a line and one by a bar.
• Funnel chart: A graphic showing the progression of a process or a flow of data. 
• Block Chart: The block chart shows a relationship between measure values as blocks. The area of each block depends on the measured value.
• Mekko chart: Mekko charts are like bar charts but with varying widths. The data is represented by bars of different sizes and widths.
• Gauge chart: The gauge chart shows the value of a single expression without any dimensions.  Gauge charts are used to measure various aspects of a business, such as the profit earned, total quantity sold, etc., using gauge meters.  By setting the maximum & minimum range of gauge meters, you can assess your performances accordingly.

QlikView objects that do not have a dimension but only have an expression are gauge charts. A gauge chart shows the value of a single expression without any dimensions. Here are some examples of gauge charts:

Trellis charts are composed of small charts (also called small multiples). It is a repetition of a chart across a grid and this grid is typically determined by the number of dimension values. A trellis chart can be used to compare metrics for different groups of data. It is included in the Visualization bundle.

Example: Below is an example of a trellis chart based on bar charts of sales data for different product categories like babywear, bath clothes, children’s wear, and so on.

Conclusion

In terms of business intelligence and data visualization, QlikView is one of the most popular and fastest-growing tools in the marketplace. In essence, QlikView is a powerful data visualization tool similar to Tableau that integrates analytics and statistics to provide a more unified view of data to help analysts and managers make informed decisions using data. The growing demand for QlikView has led companies to actively hire QlikView professionals for various roles, such as QlikView developer, Qlik Sense developer, BI analyst, QlikView application developer, Qlik Sense administrator, etc. 

In this article, we have compiled a list of top Interview Questions that are quick and insightful, and which provide ample information essential to the interview process. 

Hopefully, we have cleared up any lingering doubts or questions you may have had. Good luck with your future endeavours.

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