Automated database builds for SQL Server through a build/release pipeline are typically managed using tools that integrate with continuous integration (CI) and continuous deployment (CD) systems. Here's an overview of how this process is handled:
### 1. **Automated Database Build Process**
- **Source Control:** The database schema (DDL) and scripts (DML) are stored in source control, often using tools like Git. This can include SQL scripts or projects created using Visual Studio (SQL Server Data Tools – SSDT) or other database tools.
- **Build Pipeline:**
- **Build Definition:** A build pipeline for SQL Server usually triggers automatically upon changes to the source repository. For instance, using tools like Azure DevOps, Jenkins, or TeamCity.
- **Database Project/Schema Validation:** The pipeline uses tools like **SSDT** (SQL Server Data Tools), **Redgate SQL Change Automation**, or **Flyway** to validate and compile database projects. This ensures that the DDL is valid and ready for deployment.
- **Unit Tests for Database:** You can integrate database unit testing using tSQLt or other frameworks to ensure the new changes do not break the database.
### 2. **Database Release Process**
- **Release Pipeline:**
- The release process often consists of deploying the new DDL and DML changes to different environments (Dev, QA, Staging, and Production).
- Tools like **Redgate SQL Change Automation**, **Liquibase**, **Flyway**, or **DbUp** manage schema changes and migrations by applying incremental changesets, tracking the history of changes, and ensuring consistency across environments.
- **Rollback/Fallback Mechanism:**
- **Transaction Management:** During deployment, SQL scripts can be wrapped in transactions. If a failure occurs, the transaction is rolled back.
- **Backup Mechanism:**
- Before deployment, a full or differential database backup is often taken to enable a complete rollback if a critical failure occurs.
- **Schema Versioning and Rollbacks:** Tools like Flyway, Redgate SQL Change Automation, or Liquibase maintain a version history of database migrations. These tools allow rollback to a previous version in case of failure.
- Flyway, for example, has a `migrate` and `undo` feature, and Redgate provides a schema comparison to reverse changes.
- **Rolling Back DDL Changes:** If a DDL (e.g., table alterations) fails, reverting to the previous schema version can be handled by the version control tool, though this is complex and requires careful planning.
- **Rolling Back DML Changes:** For DML changes (e.g., data modification), compensating transactions or rollback scripts can be included to reverse any data modifications made in case of a failure.
### 3. **Handling Failures (DDL & DML)**
- **DDL Failures (Schema Changes):**
- Use **schema comparison tools** like **Redgate SQL Compare** or SSDT to identify and rollback changes if failures occur.
- **Transactional Deployment**: If possible, wrap schema changes in a transaction and roll back the transaction upon failure.
- In case of failure, either restore from a backup or use the rollback feature of tools like Liquibase or Flyway.
- **DML Failures (Data Modifications):**
- Include rollback scripts or compensating transactions to undo data changes in case of errors.
- **Pre-checks:** Always run validation queries (e.g., SELECT statements) before applying DML to ensure the data consistency is maintained.
- Use backup and restore techniques or employ log shipping to revert databases to a known good state if failures occur during DML changes.
### 4. **Tool Recommendations**
- **Redgate SQL Change Automation:** Excellent for automating deployments and managing schema changes with a focus on safety and rollback mechanisms. It integrates well with Azure DevOps, Jenkins, and other CI/CD tools.
- **Flyway:** A powerful open-source tool for database migrations with support for SQL Server. It handles versioned migrations (DDL and DML) and has rollback (`undo`) support.
- **Liquibase:** Similar to Flyway, Liquibase tracks database schema changes and supports rollbacks. It integrates with various CI/CD pipelines.
- **Azure DevOps Pipelines:** Native support for SQL Server database builds and deployments, integrates well with SSDT and Redgate tools.
- **DbUp:** A lightweight .NET-based tool for managing database migrations. It's simple and easy to integrate into build pipelines.
### Best Practices:
- Always use transactional DDL and DML scripts to ensure you can roll back in case of failures.
- Implement automated database backups before applying updates.
- Test deployments in staging environments thoroughly before pushing to production.
- Ensure that all migrations and rollback scripts are version-controlled.
This combination of tools and techniques ensures a robust, automated process for building, releasing, and rolling back changes in SQL Server databases.