Migrating from MySQL or PostgreSQL to KingbaseES can introduce subtle data loss issues, particularly with LEFT JOIN queries. This article presents a real-world case where LEFT JOIN returned fewer rows than expected after migration. It walks through the debugging process, identifies the root cause (often related to NULL handling or join order differences), and provides preventive measures. For teams undergoing database localization in China, this guide offers concrete steps to avoid similar pitfalls. The content is based on actual migration experience and includes SQL examples and testing strategies.
A practical guide to diagnosing and preventing data loss in LEFT JOIN queries during database migration to KingbaseES.