The Bridge Table Structure

Most candidates can explain what a bridge table is. The interview tests whether you can design one correctly: the schema, the weight constraint, the query pattern. Getting any of these wrong produces inflated aggregates that look plausible but are mathematically wrong. The Schema You Design in the Interview Querying Through the Bridge The Query Pattern the Interviewer Expects Walk through the result: 'Alice gets $500, Bob gets $300, Carol gets $200. Total: $1,000. Correct. The weight factor prevented the 3x inflation.' Point at the math. The interviewer is checking whether you understand that SUM(amount * weight) preserves totals while SUM(amount) without weights inflates them. The Validation Check That Signals Depth Say this unprompted: 'I would add a data quality check: SELECT order_id,