Migrating Data from SQL Server to MariaDB

Migrating data from Microsoft SQL Server to MariaDB involves careful planning and execution to ensure a smooth transition without data loss or inconsistency.

In this article, We will learn about How to migrate data from SQL Server to MariaDB by including preparation, migration steps, and validation techniques.

How to Migrate Data from SQL Server to MariaDB?

• Data migration is a critical process for organizations shifting their database infrastructure from one platform to another.
  
• SQL Server and MariaDB are both powerful relational database management systems but they have different features, data types, and licensing models.

Prerequisite

• To successfully transfer data from the SQL Server to MariaDB, access to the SQL Server database.
  
• A properly configured MariaDB Server instance and the MariaDB SQL Server extractor tool are all required.
  
• It is essential to assess the compatibility of the two databases and to plan for potential downtime and backups during the migration process.
  
• By following the guidance provided in the MariaDB migration guide, a smooth transition can be ensured.

Understanding SQL Server and MariaDB

SQL Server and MariaDB are both relational database management systems (RDBMS) but they have some fundamental differences:

1. Operating System Support:

• SQL Server: SQL Server is mainly designed to operate on Windows operating systems. While it can be run on Linux or macOS using virtualization or containers, it is not officially supported on those platforms.
• MariaDB: MariaDB is an open-source RDBMS that is designed to be cross-platform and can run on Windows, Linux, and macOS.

2. Licensing and Cost:

• SQL Server: SQL Server is a proprietary RDBMS developed and sold by Microsoft. It comes in different editions, and the cost varies depending on the edition and the number of cores/users.
• MariaDB: MariaDB is an open-source RDBMS that is free to download, use, and modify, as it is released under the GNU General Public License (GPL).

3. Data Types and Features:

• SQL Server: SQL Server supports a wide range of data types, including advanced types like geography, geometry and hierarchyid. It also offers features like stored procedures, triggers and views.
• MariaDB: MariaDB also supports a wide range of data types, but it may not have some of the advanced data types and features found in SQL Server. However, MariaDB has its own set of features, such as advanced storage engines and replication capabilities.

4. Performance and Scalability:

• SQL Server: It is known for its high performance and scalability, especially in enterprise-level applications.
• MariaDB: It is also highly scalable and performant, but may not match SQL Server's enterprise-level capabilities for very large-scale deployments.

5. Security and Compliance:

• SQL Server provides strong security features and meets various industry standards for compliance.
• MariaDB has security features, but may not have the same level of compliance and certification as SQL Server.

Preparing for the Migration

• Let's explore the evaluation of data and schema when planning for the migration from SQL Server to MariaDB. This is a important step to guarantee a seamless and successful migration process.
  
• Examine SQL Server data types, schema structures, data volumes, referential integrity, and database objects like stored procedures for compatibility with MariaDB.
  
• Develop conversion and adaptation tactics to address data type discrepancies, schema discrepancies, data complexity, and constraints.
  
• Ensure a smooth migration by considering indexing, performance factors, and modifying necessary database objects to fit MariaDB's requirements.

Step 1: Choose a Data Source

In the "Choose a Data Source" dialog, select "Microsoft SQL Server" as the data source.

This actually allows us to select and specify the source of data that you want to migrate. In this scenario it would be Microsoft SQL Server database.

Step 2: Choose a Destination

In the "Choose a Destination" dialog, select "MariaDB" as the destination.

Basically this step allows you for specifying the target database which in this case is MariaDB.

Step 3: Select Source Tables and Views

"Select source Tabless and Views" dialog, we can specify the tables and views we want to migrate from the SQL Server database.

Generating the Table and View

Here you are suppose to choose specific database objects that you want to migrate from SQL server to selected location which is MariaDB.

Step 4: Start the Migration Process

click the "Submit" button to start the migration process.

This final stage starts the migration process. The tool will review the SQL Server database, create the schema definition, data load script and configuration scripts then transfer the data to the MariaDB Server.

By following these steps, you can use the MariaDB SQL Server extraction tool to move your data from SQL Server to MariaDB smoothly and efficiently.

Example of Migrating Data and Schema from SQL Server to MariaDB

Step 1: Data Types Mapping

Example: In the SQL Server database, you have a column defined as VARCHAR(MAX). This data type does not have a direct equivalent in MariaDB. To map this, we can use the LONGTEXT data type in MariaDB, which can store text up to 4GB in size.

-- SQL Server
CREATE TABLE customers (
  id INT PRIMARY KEY,
  name VARCHAR(MAX),
  email VARCHAR(MAX)
);

-- MariaDB
CREATE TABLE customers (
  id INT PRIMARY KEY,
  name LONGTEXT,
  email LONGTEXT
);

Step 2: Schema Structures

There is a stored procedure in the SQL Server database that uses the DECIMAL(10,2) data type. The DECIMAL data type does not require precision and scale, so you would need to adjust the stored procedure definition in MariaDB.

-- SQL Server Stored Procedure
CREATE PROCEDURE CalculateTotal
  @Amount DECIMAL(10,2)
AS
BEGIN
  SELECT @Amount * 1.1 AS TotalAmount
END

-- MariaDB Stored Procedure
CREATE PROCEDURE CalculateTotal
  (IN Amount DECIMAL)
BEGIN
  SELECT Amount * 1.1 AS TotalAmount;
END

Step 3: Data Volumes and Complexity

The SQL Server database contains a large table with millions of rows and complex queries involving multiple joins. If we want to optimize performance in MariaDB, we may need to partition the table based on a frequently used column or add indexes.

-- SQL Server Table
CREATE TABLE sales (
  id INT PRIMARY KEY,
  product_id INT,
  customer_id INT,
  amount DECIMAL(10,2),
  sale_date DATE
);

-- MariaDB Table with Partitioning
CREATE TABLE sales (
  id INT PRIMARY KEY,
  product_id INT,
  customer_id INT,
  amount DECIMAL,
  sale_date DATE
)
PARTITION BY RANGE (YEAR(sale_date))
(
  PARTITION p2022 VALUES LESS THAN (2023),
  PARTITION p2023 VALUES LESS THAN (2024),
  PARTITION p2024 VALUES LESS THAN (2025)
);

-- Add Indexes
CREATE INDEX idx_sales_product ON sales (product_id);
CREATE INDEX idx_sales_customer ON sales (customer_id);

Step 4: Referential Integrity and Constraints

The SQL Server database has a table with a foreign key constraint referencing another table. In MariaDB, the syntax for defining foreign key constraints is slightly different.

- SQL Server
CREATE TABLE orders (
  id INT PRIMARY KEY,
  customer_id INT,
  CONSTRAINT fk_orders_customers FOREIGN KEY (customer_id) REFERENCES customers(id)
);

-- MariaDB
CREATE TABLE orders (
  id INT PRIMARY KEY,
  customer_id INT,
  CONSTRAINT fk_orders_customers FOREIGN KEY (customer_id) REFERENCES customers(id)
);

Step 5: Stored Procedures, Functions, and Triggers

The SQL Server database has a stored procedure that calculates the total order amount. We will need to rewrite this stored procedure using MariaDB syntax.

-- SQL Server Stored Procedure
CREATE PROCEDURE CalculateOrderTotal
  @OrderId INT
AS
BEGIN
  SELECT SUM(amount) AS TotalAmount
  FROM order_items
  WHERE order_id = @OrderId
END

-- MariaDB Stored Procedure
CREATE PROCEDURE CalculateOrderTotal
  (IN OrderId INT)
BEGIN
  SELECT SUM(amount) AS TotalAmount
  FROM order_items
  WHERE order_id = OrderId;
END

Step 6: Indexes and Performance Considerations

There is an index on the order_date column in the orders table in the SQL Server database. We may need to recreate a similar index in the MariaDB database to improve query performance.

-- SQL Server Index
CREATE INDEX idx_orders_order_date ON orders (order_date);

-- MariaDB Index
CREATE INDEX idx_orders_order_date ON orders (order_date);

Migration Tools and Techniques

Overview of Available Tools

• Database Migration Tools: Tools like Flyway, Liquibase and Rails Migrations that manage database schema changes and data migrations.
  
• ETL (Extract, Transform, Load) Tools: Tools like Talend, Informatica and Apache Airflow that facilitate data migration and integration between different sources and targets.
  
• Database Replication and Sync Tools: Tools like Debezium, Kafka Connect and AWS Database Migration Service that enable real-time data replication and synchronization.
  
• Data Migration Services: Managed services like AWS Database Migration Service, Google Cloud Data Transfer and Azure Data Migration Service that simplify large-scale data migrations.
  
• Custom Scripts and Programs: The Custom scripts and applications created with languages like Python, Java or SQL to address specific data migration needs.

5. Testing and Validation

• Ensuring the integrity of migrated data is crucial for the success of any data migration project. Key aspects to consider include schema validation to verify the correctness of table and column structures, row count validation to confirm the completeness of data transfer and checksum validation to detect any data changes.
  
• Referential integrity checks help maintain the relationships between data, while data type checks and null value validations ensure seamless conversion and preservation of data quality.
  
• Additionally, unique constraint checks and data format validations play a vital role in identifying and resolving any potential data inconsistencies.
  
• By performing a comprehensive set of these integrity checks at various stages of the migration process, organizations can have confidence in the reliability and accuracy of the data being migrated to the target system.

Conclusion

Overall, In order to migrate data from an SQL database to MariaDB, you must thoroughly assess the existing database, select an appropriate migration strategy, prepare the target MariaDB environment, and map and transform the data carefully. To ensure a successful migration to the new database platform, the actual data migration process should validate the integrity and consistency of the data.