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 error event -- unhandled connection errors crash the Node.js process)