Every year there's a new "must-learn" technology—Spark, Kafka, Databricks, Snowflake, AI, LLMs... But one skill has remained essential through every wave of innovation: SQL. When I first started learning Data Engineering, I thought SQL was just another box to check. "Learn some SELECT statements, a few JOINs, and move on to Python." I couldn't have been more wrong. The more real-world projects I worked on, the more I realized that SQL isn't just a language—it's how data eng...