api-database-mysql

# MySQL Patterns (mysql2) > **Quick Guide:** Use **mysql2/promise** for all new code -- it provides async/await support over the mysql2 callback API. Always use `createPool()` (never `createConnection()` in production) with `execute()` for parameterized queries (prepared statements, LRU-cached). Type query results with `RowDataPacket` generics for SELECTs and `ResultSetHeader` for INSERT/UPDATE/DELETE. For transactions, acquire a dedicated connection with `pool.getConnection()`, wrap in try/finally to guarantee `connection.release()`. Never interpolate user input into SQL strings -- always use `?` placeholders. Handle `ER_DUP_ENTRY` and `ER_LOCK_DEADLOCK` explicitly in catch blocks. --- <critical_requirements> ## CRITICAL: Before Using This Skill > **All code must follow project conventions in CLAUDE.md** (kebab-case, named exports, import ordering, `import type`, named constants) **(You MUST use `execute()` with `?` placeholders for ALL queries containing user input -- NEVER interpolate values into SQL strings with template literals or string concatenation)** **(You MUST use `pool.getConnection()` for transactions and release the connection in a `finally` block -- pool convenience methods (`pool.execute()`) use a different connection per call and cannot maintain transaction state)** **(You MUST always import from `mysql2/promise` for async/await code -- the base `mysql2` module returns callback-based objects that do not support `await`)** **(You MUST handle the pool...