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Partitioning tables is an effective strategy for managing large databases. By dividing a table into smaller, more manageable parts, you can improve query performance and make maintenance tasks more efficient. The partitioning strategy you choose largely depends on your application's specific requirements, but a common approach is to partition data by date, known as partitioned tables with monthly roll-off. In this blog post, we'll discuss how to design partitioned tables with monthly roll-off using SQL Server 2012, SQL Server 2014, MySQL 5.6, DB2 10.5, and Azure SQL.

The first step is to create a partition function. This defines how the table's data will be divided. In SQL Server, you can create a partition function using the CREATE PARTITION FUNCTION statement. For example, to create a partition function that partitions a table into 12 partitions based on the month of a date column, you could use the following T-SQL code:

-- T-SQL code
CREATE PARTITION FUNCTION PF_Monthly (datetime)
AS RANGE RIGHT FOR VALUES (
    '2015-01-01', 
    '2015-02-01', 
    '2015-03-01',
    '2015-04-01',
    '2015-05-01',
    '2015-06-01',
    '2015-07-01',
    '2015-08-01',
    '2015-09-01',
    '2015-10-01',
    '2015-11-01'
)

In MySQL, partitioning a table by month can be done using the PARTITION BY RANGE statement. The TO_DAYS function can be used to convert the date to a number that represents the number of days since year 0. Here is an example:

-- MySQL code
CREATE TABLE orders (
    order_id INT NOT NULL,
    order_date DATE NOT NULL
)
PARTITION BY RANGE(TO_DAYS(order_date)) (
    PARTITION p0 VALUES LESS THAN (TO_DAYS('2015-02-01')),
    PARTITION p1 VALUES LESS THAN (TO_DAYS('2015-03-01')),
    PARTITION p2 VALUES LESS THAN (TO_DAYS('2015-04-01')),
    PARTITION p3 VALUES LESS THAN (TO_DAYS('2015-05-01')),
    PARTITION p4 VALUES LESS THAN (TO_DAYS('2015-06-01')),
    PARTITION p5 VALUES LESS THAN (TO_DAYS('2015-07-01')),
    PARTITION p6 VALUES LESS THAN (TO_DAYS('2015-08-01')),
    PARTITION p7 VALUES LESS THAN (TO_DAYS('2015-09-01')),
    PARTITION p8 VALUES LESS THAN (TO_DAYS('2015-10-01')),
    PARTITION p9 VALUES LESS THAN (TO_DAYS('2015-11-01')),
    PARTITION p10 VALUES LESS THAN (TO_DAYS('2015-12-01')),
    PARTITION p11 VALUES LESS THAN (TO_DAYS('2016-01-01'))
)

Once the partition function is defined, you can then create a partition scheme. The partition scheme maps the partitions defined by the partition function to filegroups. A filegroup is a logical unit that groups files used for database storage. Here's how you would create a partition scheme in SQL Server:

-- T-SQL code
CREATE PARTITION SCHEME PS_Monthly
AS PARTITION PF_Monthly
ALL TO ([PRIMARY])

Finally, you create the table using the partition scheme. In SQL Server, you can do this using the ON clause in the CREATE TABLE statement. In MySQL, you can do this by specifying the PARTITION BY clause in the CREATE TABLE statement, as shown earlier. In DB2, you would use the PARTITION BY RANGE statement in the CREATE TABLE statement. In Azure SQL, the process is similar to SQL Server, as Azure SQL is based on the SQL Server technology.

By partitioning your tables by month, you can significantly improve the performance of your queries and make your database easier to manage. However, keep in mind that partitioning is not a magic bullet. It can introduce complexity and overhead, so it's important to thoroughly test your partitioned tables to ensure they provide the benefits you expect.