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A focused guide to window functions in BigQuery — cumulative sums, rolling averages, ranking functions, named windows, RANGE frames, and more.
Even an “empty” STRUCT is still technically something. Not the same as a standalone NULL value. This is why, if you work with STRUCTs in SQL and try to find the latest non-empty struct using LAST_VALUE(...) IGNORE NULLS, you’ll notice it doesn’t help...
Haven’t posted all summer, but this bug pulled me straight out of the shadows. I recently faced a mystery that pushed me to the edge of despair. It seemed like a simple issue at first glance. A report kept changing completely at random. I spent a goo...
Here’s a quick BigQuery SQL exercise. I often work with cumulative aggregations, but it’s not every day that I need to reverse them—converting cumulative values back into monthly figures. Let's look at an example. The dataset provides cumulative sale...
If you’re like me, you probably use QUALIFY + ROW_NUMBER() almost daily for deduplication or finding the first/last occurrence of something. It’s a powerful combo in modern SQL ! But here’s the catch: there are subtle nuances and edge cases that can ...
Here's something I found out about the ORDER BY clause in BigQuery SQL the other day. Check out the NULLS FIRST / NULLS LAST clauses. What do they do? They control how to treat NULL values when sorting. While these are entirely optional, they're actu...
How to compute a rolling period calculation in BigQuery? In one of my previous posts, I've showcased using RANGE inside window function declarations in the context of computing a cumulative sum. Today we're going to look at another example often foun...
