data analyst

How to Fix a Slow SQL Query: A Practical Guide for Data Analysts

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There is a specific kind of silence that happens when you run a query in front of someone. The spinner turns. You start talking to fill the gap. You mention that the table is quite large. Two minutes later you are apologising. Most slow queries are not slow because the database is weak or because … Read more

SQL Window Functions: The Thing That Separates Beginner Queries From Analyst Queries

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There is a moment in most analysts’ careers where they stop writing SQL that works and start writing SQL that is good. For a lot of people, that moment is window functions. Before you learn them, certain problems feel genuinely impossible in SQL. Rank each salesperson within their region. Show each month alongside the previous … Read more