28 February 2022 Fan and chasm traps in Qlik Sense Share this message Every Friday at Bitmetric we’re posting a new Qlik certification practice question to our LinkedIn company page. Last Friday we asked the following Qlik Data Architect certification practice question about a sales and budget model. In reality, we wanted to teach you about fan and chasm traps in Qlik. This week’s question has triggered an almost unanimous response. The correct answer is D: budgets cannot be shown for customers who haven’t bought anything We can verify this by loading a small dataset and see what happens. In the following set we have two customers, A and B. Customer A has sales amounts of 50 and 100, and a budget of 200. Customer B has no sales and a budget of 200. If we load this data into Qlik Sense and visualize it in a table we see the following result: We can clearly see that there is no association between Customer ID B, on row 3, and the Budget Amount 200, on row 4. The reason for this is the way the data is modelled: The CUSTOMER table is associated with the SALES table through the Customer ID field. In turn, the SALES table is associated with the BUDGET table through the Budget ID field. As Customer ID B does not have any sales, it’s missing the ‘hop’ between the CUSTOMER and BUDGET table. Only once Customer ID B has entries in the SALES table will the data be correctly associated. This issue is known as a ‘Chasm trap‘, where a model may suggest the existence of a relationship between entities (in this case, CUSTOMER and BUDGET), but the pathway does not exist for certain entity occurrences (in this case, Customer ID B). OK, so the correct answer is D, but isn’t C also correct? If you come from an SQL background you may expect that budgets get multiplied for customers who have multiple sales. This issue is known as a ‘Fan trap’ and it would be a correct assumption if we were to JOIN the tables together. In this data model however, that is not the case. This article by Henric Cronström explains it very well. Henric also gives an additional example of a Chasm trap, and a suggestion on how to resolve it. How can we model this correctly? Now that we know what the issue is, how can we model this data correctly so that customers, sales and budget are all correctly related? We’ll leave that topic for another time, although we’re certainly interested in your take on it 😉 We look forward to seeing your comments and hope to see you again next Friday! More from the Bitmetric team Take your Qlik skills to the next level! Since 2013, the Masters Summit for Qlik is the premier advanced training for Qlik. Join us in Vienna and take your Qlik skills to the next level. Join the team! Enjoying these challenges? We have many more, and we’ll even pay you to solve them 😉 Check out our job opening. Data Model Friday Qlik Test Prep Solution How can we help? Barry has over 20 years experience as a Data & Analytics architect, developer, trainer and author. He will gladly help you with any questions you may have. Call us Mail us 25 April 2024 Over 3000 Qlik Sense servers still vulnerable to Cactus ransomware In November of last year we reported on how two critical vulnerabilities in Qlik Sense Enterprise for Windows were exploited in the Cactus ransomware campaign. As of today, over 3000 vulnerable Qlik Sense servers remain connected to the Internet. New Release Qlik Vulnerability 29 March 2024 Dealing with missing and late arriving values with OtherSymbol and other solutions Learn effective strategies for handling missing or late-arriving dimension values in Qlik with our expert guide. Discover how to use OtherSymbol, WHERE NOT EXISTS, and other solutions to deal with early-arriving facts Data Model Friday Qlik Test Prep Qlik Solution 22 March 2024 Picking the right color palette for your visualization Discover how to choose the perfect color palette for your data visualizations with our expert guide. Learn about single, categorical, sequential, and diverging color palettes to enhance your charts and graphs. Ideal for data analysts and visualizers. Friday Qlik Test Prep Qlik SenseTheme Visualization
25 April 2024 Over 3000 Qlik Sense servers still vulnerable to Cactus ransomware In November of last year we reported on how two critical vulnerabilities in Qlik Sense Enterprise for Windows were exploited in the Cactus ransomware campaign. As of today, over 3000 vulnerable Qlik Sense servers remain connected to the Internet. New Release Qlik Vulnerability
29 March 2024 Dealing with missing and late arriving values with OtherSymbol and other solutions Learn effective strategies for handling missing or late-arriving dimension values in Qlik with our expert guide. Discover how to use OtherSymbol, WHERE NOT EXISTS, and other solutions to deal with early-arriving facts Data Model Friday Qlik Test Prep Qlik Solution
22 March 2024 Picking the right color palette for your visualization Discover how to choose the perfect color palette for your data visualizations with our expert guide. Learn about single, categorical, sequential, and diverging color palettes to enhance your charts and graphs. Ideal for data analysts and visualizers. Friday Qlik Test Prep Qlik SenseTheme Visualization