Sql

You run a query to get total revenue per customer. Customer #1 should have $500 in orders. Your query says $1,500. The raw data checks out. So what is wrong here? You just hit the fan trap — a sneaky SQL join issue that multiplies your numbers without any warning. Let me show you how it happens and how to fix it. 🤔 What Is the Fan Trap? The fan trap happens when you join tables along a one-to-many relationship and then aggregate. The “many” side fans out the rows from the “one” side, duplicating them before your SUM or COUNT ever runs. ...

You run a query to calculate total sales for Order #1. The result shows 16 items sold when your customer only bought 8. You check the database - the raw data is correct. So why is your query playing mind games? Welcome to the chasm trap. It’s a data modeling issue that silently doubles (or triples, or worse) your aggregation results. Let me show you exactly what’s happening and how to fix it. ...