Temporal tables in SQL Server provide a powerful way to track historical data changes. However, when it comes to clearing out data from these tables, the standard TRUNCATE statement doesn’t work the same as it does on normal (non-temporal) tables.
This article will guide you through the process of truncating a temporal table while maintaining its integrity.
Continue readingTemporal tables, introduced in SQL Server 2016, provide a powerful mechanism for tracking historical changes to data. This feature is particularly useful for auditing purposes, allowing organisations to maintain a complete history of data modifications without the need for complex triggers or custom logging solutions.
In this article, we’ll explore how to implement and use temporal tables for auditing in SQL Server, along with examples to demonstrate.
Continue readingThe WHILE loop in SQL Server is a control-flow statement that allows us to repeatedly execute a block of code as long as a specified condition is true. It’s useful for iterative tasks and processing data in batches.
In MySQL, the event_scheduler system variable is used to start and stop the Event Scheduler, as well as enable or disable it.
At runtime we can set the value to ON or OFF, and we can check the current value of the variable. We can also disable the Event Scheduler at server startup, but we can’t do this at runtime. However, we can still check the event_scheduler variable to see whether it’s enabled or disabled.
Most SQL databases have a handful of “ranking” functions that allow us to rank data. By “handful”, I mean there’s a common set of around six SQL rank functions that most of the major RDBMSs appear to support.
SQL rank functions allow us to assign ranks or row numbers to result sets.
Continue readingWhile INNER and LEFT JOINs are the workhorses of SQL queries, T-SQL offers several more advanced join techniques that can be invaluable for complex data analysis and manipulation. This article explores some of these powerful join methods and how they can enhance our queries.
Below are the string literal date formats that SQL Server supports for the datetime2 data type. These are the formats that we can provide when setting a datetime2 date from a string literal.
Continue readingIn MySQL we can use the CREATE EVENT statement to create scheduled events. As with many CREATE ... statements, we have the option of using the IF NOT EXISTS clause to specify that the object should only be created if it doesn’t already exist.
Of course, we wouldn’t normally be trying to create an event if we know that it already exists. But there may be times where we’re not sure, and we want our code to handle this scenario without throwing an error if an event with the same name already exists. This is common when creating scripts that are designed to be run across multiple environments. That’s where the IF NOT EXISTS clause can come in handy.
When we create a scheduled event in MySQL, we have the option of adding a comment to the event. This comment can be a string of up to 64 characters. We have a couple of options when it comes to viewing the comment of an existing event.
Continue readingIn MySQL we can use the ALTER EVENT statement to make changes to existing scheduled events, including changing the name of the event.