116Explain the Kalman filter and state-space models. What are the predict and update steps actually doing?▼hardNVIDIAAppleUber1 replies◆ premiumThe Kalman filter is optimal Bayesian tracking under linear-Gaussian assumptions, and it is two steps repeated forever. The signal is explaining what the gain trades off and when the assumptions break. Here is the answer.Open full answer →
31What is the QUALIFY clause, and how does it simplify filtering on window functions?▼mediumSnowflakeDatabricksGoogle1 replies◆ premiumYou cannot filter on a window function in WHERE, so people wrap queries in subqueries. QUALIFY filters window results directly. The signal is knowing why WHERE cannot do it and writing top-N-per-group cleanly.Open full answer →
