Introduction
Temporal tables in SQL Server provide an effective way to manage historical data, allowing you to track changes in your data over time. In this blog post, we’ll explore the concept of temporal tables and discuss how to implement them in SQL Server. Additionally, we’ll create a table-driven stored procedure to automate the deletion of records from the main table based on a specified time limit stored in a configuration table.
Understanding Temporal Tables
Temporal tables, introduced in SQL Server 2016, enable you to keep track of changes in data by maintaining historical versions of rows. This is particularly useful for auditing purposes, compliance requirements, or analyzing historical trends. Temporal tables consist of two parts: the main table (current table) and the history table.
Current Table: This table holds the most recent version of the data.
History Table: This table stores the historical versions of the data, including the start and end timestamps for each version.
Implementing Temporal Tables
To create a temporal table, you need to define the history table and enable the temporal feature on the main table. Here’s an example of how you can create a temporal table:
In the above example, ValidFrom and ValidTo columns define the period for which each version of the row is valid.
Automating Record Deletion with Table-Driven Stored Procedure
Now, let’s create a table-driven stored procedure to delete records from the main table when they exceed a specified time limit. Assume we have a configuration table named RetentionConfig with columns TableName and RetentionDays.
We can create a stored procedure to delete records based on the configuration as follows:
In this stored procedure:
We use a cursor to iterate through the RetentionConfig table.
For each table, we calculate the cutoff date based on the retention period and construct a dynamic SQL query to delete records before that date.
The sp_executesql system stored procedure is used to execute the dynamic SQL query.
Conclusion
Temporal tables in SQL Server offer a robust solution for managing historical data, enabling you to track changes effectively. By combining temporal tables with a table-driven stored procedure, you can automate the process of purging old records based on configurable retention periods, ensuring that your database stays optimized and compliant with data retention policies.