chore: add CLAUDE.md

Author: tianzhou

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+This is a GitOps demonstration repository for database CI/CD using Bytebase and GitHub Actions with GitHub Flow. The repository shows how to integrate database schema changes with application deployment pipelines.
+
+## Repository Structure
+
+- `migrations-semver/`: Contains SQL migration files following semantic versioning naming convention (e.g., `1.0.0_init.sql`, `1.1.1_comment.sql`)
+- `schema/`: Contains base database schema definitions
+- `.github/workflows/`: GitHub Actions workflows for CI/CD pipeline
+
+## Migration File Naming
+
+Migration files MUST follow semantic versioning pattern: `{major}.{minor}.{patch}_{description}.sql`
+- Examples: `1.0.0_init.sql`, `1.1.1_comment.sql`, `1.13.0_phone.sql`
+- Files are processed by Bytebase in semantic version order
+
+## GitHub Actions Workflows
+
+### SQL Review Workflow (`sql-review-action.yml`)
+- Triggers on pull requests to `main` branch when `migrations-semver/*.sql` files change
+- Uses `bytebase/bytebase-action:latest` Docker image
+- Runs SQL validation against production database
+- Requires `BYTEBASE_SERVICE_ACCOUNT_SECRET` repository secret
+
+### Release Workflow (`release-action.yml`)
+- Triggers on push to `main` branch when `migrations-semver/*.sql` files change
+- Three-stage process:
+  1. `build`: Mock application build step
+  2. `create-rollout`: Creates Bytebase rollout plan for both test and prod databases
+  3. `deploy-to-test`: Deploys to test environment automatically
+  4. `deploy-to-prod`: Deploys to production (requires manual approval via GitHub environment protection)
+
+## Environment Configuration
+
+Both workflows use these environment variables:
+- `BYTEBASE_URL`: Bytebase instance URL
+- `BYTEBASE_SERVICE_ACCOUNT`: Service account email
+- `BYTEBASE_SERVICE_ACCOUNT_SECRET`: Service account password (stored in GitHub secrets)
+- `BYTEBASE_PROJECT`: Target Bytebase project
+- `BYTEBASE_TARGETS`: Comma-separated list of database targets
+- `FILE_PATTERN`: Glob pattern for migration files (`migrations-semver/*.sql`)
+
+## Database Schema
+
+The schema includes:
+- Employee management system with tables: `employee`, `department`, `dept_manager`, `dept_emp`, `title`, `salary`
+- Audit logging system with trigger-based change tracking
+- Views for current department assignments
+
+## Development Workflow
+
+1. Create feature branch
+2. Add SQL migration files to `migrations-semver/` with proper semantic versioning
+3. Create pull request - triggers SQL review workflow
+4. Merge to main - triggers release workflow
+5. Test environment deployment happens automatically
+6. Production deployment requires manual approval through GitHub environment protection
+
+## Key Integration Points
+
+- All database changes go through Bytebase for review and deployment
+- GitHub environment protection rules control production deployments
+- Migration files are validated against actual database schemas during PR review