using-mysql-connector

name	using-mysql-connector
description	Implements MySQL database connections, SQL queries, and data operations using generated clients and MCP tools. Use when doing ANYTHING that touches MySQL in any way, load this skill.

Major Platform Resource: MySQL

Common: Interacting with Resources

Security: Never connect directly to databases/APIs. Never use credentials in code. Always use generated clients or MCP tools.

Two ways to interact with resources:

1. MCP tools (direct, no code needed): Tools follow the pattern mcp__resources__<resourcetype>_<toolname>. Use mcp__resources__list_resources to discover available resources and their IDs.
2. Generated TypeScript clients (for app code): Call mcp__resource-tools__add-resource-client with a resourceId to generate a typed client. Clients are created in /clients/ (Next.js) or /src/clients/ (Vite).

CRITICAL: Do NOT guess client method names or signatures. The TypeScript clients in @major-tech/resource-client have strongly typed inputs and outputs. ALWAYS read the actual client source code in the generated /clients/ directory (or the package itself) to verify available methods and their exact signatures before writing any client code.

Framework note: Next.js = resource clients must be used in server-side code only (Server Components, Server Actions, API Routes). Vite = call directly from frontend.

Error handling: Always check result.ok before accessing result.result.

Invocation keys must be static strings — use descriptive literals like "fetch-user-orders", never dynamic values like `${date}-records`.

---

MCP Tools

• mcp__resources__mysql_query — Execute a read-only MySQL query. Supports SELECT and introspection statements like SHOW TABLES, DESCRIBE table_name, SHOW DATABASES, SHOW CREATE TABLE table_name, and EXPLAIN. Does not require user approval — prefer this tool for all read-only operations. Args: resourceId, statement, params?, description, timeoutMs?
• mcp__resources__mysql_invoke — Execute any SQL statement including write operations (INSERT, UPDATE, DELETE, CREATE TABLE, ALTER TABLE, DROP, etc.). Returns rows and rowsAffected. Requires user approval — only use when you need to write data. Args: resourceId, sql, params?, description, timeoutMs?

IMPORTANT: Always use mysql_query for read-only operations. It does not require user approval, making the workflow faster and smoother. Only use mysql_invoke when you actually need to perform writes (INSERT, UPDATE, DELETE, DDL). Never use mysql_invoke for SELECT queries or schema exploration.

TypeScript Client

import { myMysqlClient } from "./clients";

// invoke<T>(sql, params?, invocationKey, timeoutMs?)
// Uses positional ? placeholders
const result = await myMysqlClient.invoke<{ id: number; name: string }>(
	"SELECT * FROM users WHERE id = ?",
	[userId],
	"fetch-user",
);
if (result.ok) {
	console.log(result.result.rows);
}

Tips

• Use mysql_query exclusively for read-only tasks. Never use mysql_invoke for read-only.
• Uses positional ? placeholders — not $1, $2 like PostgreSQL or @name like MSSQL. The first ? maps to params[0], the second to params[1], etc.
• Default port is 3306
• Use mysql_query with SHOW DATABASES, SHOW TABLES, DESCRIBE table_name, SHOW CREATE TABLE table_name, SHOW INDEX FROM table_name to explore database structure
• JSON columns (MySQL 5.7+) are returned as parsed objects, not raw strings
• Use backticks (`) for identifiers (table/column names), single quotes for string values
• LIMIT n for pagination (not FETCH FIRST n ROWS ONLY). For offset: LIMIT offset, count or LIMIT count OFFSET offset
• Table names are case-sensitive on Linux, case-insensitive on macOS/Windows — always use exact case from the schema

Docs: MySQL 8.0 Reference Manual