15 QlikView Interview Questions and Answers

QlikView is a powerful business intelligence and data visualization tool that enables organizations to transform raw data into meaningful insights. Known for its associative data model and user-friendly interface, QlikView allows users to explore data intuitively and make data-driven decisions. Its robust features and flexibility make it a preferred choice for many companies looking to enhance their data analytics capabilities.

This article aims to prepare you for interviews by providing a curated selection of QlikView-related questions and answers. By familiarizing yourself with these questions, you will gain a deeper understanding of QlikView’s functionalities and be better equipped to demonstrate your expertise during the interview process.

QlikView Interview Questions and Answers

1. Describe the process of loading data from an Excel file into QlikView.

To load data from an Excel file into QlikView, follow these steps:

• Open QlikView and create a new document or open an existing one.
• Go to the “Script Editor” by clicking on the “Edit Script” button.
• In the “Script Editor,” click on the “Table Files” button to open the “File Wizard.”
• Browse and select the Excel file you want to load.
• The “File Wizard” will display the data from the Excel file. You can choose the specific sheet and range of cells you want to load.
• Click “Next” and then “Finish” to generate the script for loading the data.
• Click “Reload” to execute the script and load the data into QlikView.

2. Explain how section access works and how you would implement it in a QlikView application.

Section access in QlikView is implemented by defining a special section in the script where access rights are specified. This section includes fields such as USERID, PASSWORD, ACCESS, and REDUCTION fields. The REDUCTION field links the section access table to the data model, allowing for dynamic data reduction based on user credentials.

Example:

SECTION ACCESS;
LOAD * INLINE [
    ACCESS, USERID, PASSWORD, REDUCTION
    ADMIN, admin, admin123, *
    USER, user1, user123, 1
    USER, user2, user456, 2
];

SECTION APPLICATION;
LOAD * INLINE [
    REDUCTION, DataField
    1, Data for User 1
    2, Data for User 2
];

To implement section access, define the section access table in the script, link it to the main data model using a common field, and reload the script.

3. Write an expression to calculate the year-over-year growth rate in a chart.

Year-over-year (YoY) growth rate measures the annual growth rate of a metric. In QlikView, you can calculate it using set analysis and the Above function.

Example expression:

(Sum(Sales) - Above(Sum(Sales), 12)) / Above(Sum(Sales), 12)

This expression calculates the difference between the current period’s sales and the previous year’s sales, divided by the previous year’s sales.

4. Describe the steps involved in setting up an incremental load for a large dataset.

Setting up an incremental load in QlikView involves:

1. Identify the Incremental Load Strategy: Determine criteria for identifying new or updated records.
2. Extract New or Updated Data: Modify the data extraction script to pull only new or updated records.
3. Store Historical Data: Maintain a QVD file to store historical data.
4. Merge Data: Combine newly extracted data with historical data.
5. Update QVD File: Save the merged dataset back into the QVD file.
6. Handle Deletions: Implement a mechanism to identify and remove deleted records.

Example script snippet:

// Load historical data
HistoricalData:
LOAD *
FROM HistoricalData.qvd (qvd);

// Load new or updated data
NewData:
SQL SELECT *
FROM SourceTable
WHERE LastModified > '$(LastLoadTime)';

// Concatenate new data with historical data
Concatenate (HistoricalData)
LOAD *
RESIDENT NewData;

// Store the updated data back into the QVD file
STORE HistoricalData INTO HistoricalData.qvd (qvd);

5. How would you create a master calendar in QlikView, and why is it useful?

A master calendar in QlikView is a centralized date table that includes all possible dates within a given range. It ensures consistency in date-related fields, simplifying time-based analysis and reporting.

Example:

// Define the date range
LET vMinDate = Num(MakeDate(2020, 1, 1));
LET vMaxDate = Num(Today());

// Generate the master calendar
MasterCalendar:
LOAD
    Date($(vMinDate) + IterNo() - 1) AS Date,
    Year(Date($(vMinDate) + IterNo() - 1)) AS Year,
    Month(Date($(vMinDate) + IterNo() - 1)) AS Month,
    Day(Date($(vMinDate) + IterNo() - 1)) AS Day,
    WeekDay(Date($(vMinDate) + IterNo() - 1)) AS WeekDay,
    'Q' & Ceil(Month(Date($(vMinDate) + IterNo() - 1)) / 3) AS Quarter
AUTOGENERATE 1 WHILE $(vMinDate) + IterNo() - 1 <= $(vMaxDate);

6. How would you use the Aggr function to perform a nested aggregation in a chart?

The Aggr function in QlikView allows for nested aggregations by creating a temporary table of results from an initial aggregation, which can then be used for further aggregation.

Example:

Max(Aggr(Avg(Sales), ProductCategory))

This calculates the average sales per product category and finds the maximum of these averages.

7. Describe the purpose of link tables and how you would implement one in a QlikView data model.

Link tables in QlikView resolve synthetic keys and circular references by consolidating common fields into a single table.

To implement a link table:

• Identify common fields causing synthetic keys or circular references.
• Create a link table with these fields.
• Remove common fields from original tables and replace them with a single key field linking to the link table.
• Load the link table into the data model.

Example:

LOAD
    CustomerID,
    ProductID,
    OrderID
FROM
    Orders.qvd (qvd);

LOAD
    CustomerID,
    CustomerName,
    CustomerAddress
FROM
    Customers.qvd (qvd);

LOAD
    ProductID,
    ProductName,
    ProductCategory
FROM
    Products.qvd (qvd);

LinkTable:
LOAD
    CustomerID,
    ProductID,
    OrderID
RESIDENT Orders;

DROP FIELDS CustomerID, ProductID FROM Orders;

8. Provide an example of an advanced scripting technique you have used in QlikView.

In QlikView, advanced scripting techniques enhance data transformation. The ApplyMap function efficiently maps values from one table to another.

Example:

// Creating a mapping table
MappingTable:
MAPPING LOAD
    OldValue,
    NewValue
FROM
    MappingFile.csv (txt, utf8, embedded labels, delimiter is ',');

// Using ApplyMap to transform data
Data:
LOAD
    Field1,
    ApplyMap('MappingTable', Field2, 'Unknown') AS MappedField2
FROM
    DataFile.csv (txt, utf8, embedded labels, delimiter is ',');

In this example, the ApplyMap function replaces values in Field2 with corresponding values from the mapping table.

9. What are QVD files, and how do they benefit a QlikView application?

QVD (QlikView Data) files are a proprietary format used by QlikView to store data. They are optimized for reading and writing operations, making them beneficial for any QlikView application.

Benefits include:

• Performance: QVD files are optimized for fast data loading.
• Storage Efficiency: Data is compressed, saving disk space.
• Incremental Load: Supports loading only new or changed data.
• Data Sharing: Can be shared across multiple applications.
• Backup and Recovery: Serve as a backup of the data.

10. How would you perform a complex join between multiple tables in QlikView?

In QlikView, performing a complex join between multiple tables involves using the script editor to load and manipulate data. For more complex joins, use specific join operations such as inner join, left join, right join, and outer join.

Example:

LOAD
    CustomerID,
    CustomerName
FROM
    Customers.qvd (qvd);

LEFT JOIN (Customers)
LOAD
    CustomerID,
    OrderID,
    OrderDate
FROM
    Orders.qvd (qvd);

INNER JOIN (Orders)
LOAD
    OrderID,
    ProductID,
    Quantity
FROM
    OrderDetails.qvd (qvd);

This example demonstrates a left join with the Orders table and an inner join with the OrderDetails table.

11. How would you integrate QlikView with another tool, such as R or Python, to enhance its functionality?

Integrating QlikView with tools like R or Python enhances its functionality by leveraging advanced analytical capabilities. QlikView supports integration through various connectors and APIs.

For R, QlikView provides the Advanced Analytics Integration (AAI) to call R scripts directly. For Python, use the Server Side Extension (SSE) to call Python functions from within QlikView.

Both integrations involve setting up a server-side service that QlikView can communicate with, executing the R or Python code, and returning results to QlikView.

12. What are some best practices for data visualization in QlikView?

When creating data visualizations in QlikView, adhere to best practices for effective information conveyance:

• Clarity and Simplicity: Ensure visualizations are easy to understand.
• Appropriate Chart Types: Choose the right chart type for your data.
• Consistent Color Schemes: Use consistent colors to avoid confusion.
• Effective Use of Labels and Legends: Provide context and ensure readability.
• Interactivity: Leverage interactive features for data exploration.
• Data Accuracy: Ensure data is accurate and up-to-date.
• Focus on Key Metrics: Highlight relevant metrics and insights.

13. How do you handle large datasets efficiently in QlikView?

Handling large datasets efficiently in QlikView involves several strategies:

• Data Reduction: Filter out unnecessary data using WHERE clauses.
• Efficient Data Modeling: Design a star or snowflake schema.
• Incremental Load: Update only changed or new data.
• Optimized Expressions: Use optimized expressions and pre-calculate values.
• Memory Management: Monitor and manage memory usage.
• Data Compression: Utilize data compression features.
• Use of QVD Files: Store pre-processed data in QVD files.

14. What security best practices do you follow when developing QlikView applications?

When developing QlikView applications, follow security best practices to protect data:

• Data Access Control: Implement strict data access controls.
• User Authentication: Use robust authentication mechanisms.
• Data Encryption: Encrypt sensitive data at rest and in transit.
• Application Security Settings: Configure server and publisher settings.
• Audit and Monitoring: Implement logging and monitoring.
• Least Privilege Principle: Grant users the minimum level of access required.
• Regular Security Reviews: Conduct regular security reviews and assessments.

15. How do you troubleshoot and resolve common issues in QlikView applications?

To troubleshoot and resolve common issues in QlikView applications, follow these steps:

1. Data Load Errors:

• Check the script for syntax errors.
• Verify data source connections and credentials.
• Ensure that the data source is available and accessible.
• Use the QlikView debugger to step through the script and identify where the error occurs.

2. Performance Issues:

• Optimize data models by removing unnecessary fields and tables.
• Use appropriate data types and avoid excessive use of calculated fields.
• Implement incremental data loads to reduce the amount of data processed.
• Monitor system resources and ensure that the server has adequate memory and CPU capacity.

3. Script Errors:

• Review the script for logical errors and correct them.
• Use comments to document the script and make it easier to understand.
• Test the script in smaller sections to isolate and identify issues.
• Utilize QlikView’s built-in functions and error handling mechanisms to manage exceptions.

4. User Access and Security:

• Verify that users have the appropriate permissions to access the application and data.
• Check section access settings to ensure that they are correctly configured.
• Review the security settings in the QlikView Management Console (QMC) to ensure compliance with organizational policies.

5. Visualization and Dashboard Issues:

• Ensure that visualizations are correctly configured and that data is properly linked.
• Check for any missing or incorrect expressions in charts and tables.
• Validate that the layout and design of the dashboard meet user requirements and are user-friendly.