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With the rise of globalization, more and more businesses are leveraging the power of data worldwide. Consequently, it is becoming increasingly crucial to manage and support databases that serve customers across different time zones. This post will provide a guide on maintaining time zones in global SQL Server databases, using technology from SQL Server 2016, SQL Server 2017, MySQL 5.7, DB2 11.1, and Azure SQL.

SQL Server 2016 introduced the AT TIME ZONE feature, which simplifies the conversion of a datetime value from one time zone to another. This function takes the source time zone and the target time zone as parameters and returns the datetime value in the target time zone. The following is a T-SQL example:

DECLARE @dt datetime2 = '2018-01-01T00:00:00'
SELECT @dt AT TIME ZONE 'Pacific Standard Time' AT TIME ZONE 'Eastern Standard Time'

SQL Server 2017 continues to support this feature, allowing developers to maintain consistency across time zones. It is essential to note that the AT TIME ZONE function works based on the time zone offset from UTC, and not daylight saving changes. Therefore, it may not return accurate results for dates that fall within the daylight saving period.

MySQL 5.7 offers a different approach. It allows you to set the system time zone for the database server using the --default-time-zone option. It also provides named time zones, which are more flexible as they automatically adjust for daylight saving time. Here is an example of how to set the time zone in MySQL:

SET GLOBAL time_zone = 'America/New_York';

DB2 11.1 also supports time zone conversions. It provides the TO_DATE function that can convert a timestamp from one time zone to another. However, it is crucial to remember that, similar to SQL Server, DB2 does not consider daylight saving time during the conversion.

Azure SQL, Microsoft's cloud-based database service, adheres to the same time zone handling principles as SQL Server. It supports the AT TIME ZONE function for time zone conversions. However, in Azure, the default time zone for a database is set at the server level and cannot be changed at the database level.

In conclusion, maintaining time zones in global SQL Server databases can be a complex task, but it is crucial for ensuring accurate data handling and reporting. By understanding and utilizing the features provided by each SQL technology, developers can effectively manage time zones in their databases, irrespective of the geographical locations of their users.