New Interview Questions: February 2026
Questions added to the Dataford question bank in February 2026, ranked by how often they are asked in real interviews.
Explain INNER JOIN vs LEFT JOIN semantics, NULL behavior, and common pitfalls (filters turning LEFT into INNER) using real analytics examples.
AIG Claims
NCR
TargetbaseCompute daily agent call KPIs and SLA using joins, aggregations, and window ranking in a contact center model.
ADPReconcile a Power BI revenue KPI to source-of-truth payments using joins, aggregations, and window functions.
The Johns Hopkins UniversityExplain C++ memory ownership, RAII, smart pointers, and common failure modes like leaks and use-after-free.
Waymo
Northrop Grumman
CATERPILLARCompute a lexicographically smallest topological order of tasks; return [] if the dependency graph has a cycle.
AmazonParse and evaluate a restricted JS-like assertion string using a stack-based expression parser.
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Compute per-variant sample size and runtime to detect a 0.6pp checkout conversion lift with 80% power at α=0.05.
DONE by NONETaskRabbit
VanguardCompute and interpret a two-proportion z-test p-value for a checkout A/B test, and explain what the p-value does not mean.
payactiv