I have a blog post series about some nice features in the Snowflake cloud data warehouse; one of them is about the IS [NOT] DISTINCT FROM predicate. I was excited to find out this is now also included in the T-SQL language since the SQL Server 2022 CTP 2.1 preview! You can find the official documentation here.
A quick recap: IS [NOT] DISTINCT FROM allows you to compare two expressions (much like = and <>), but this predicate takes NULL values into account. Basically, it’s a shorter way to write the following:
SELECT * FROM dbo.FactInternetSales WHERE OrderDate = ISNULL(@orderdate,'1900-01-01');
Previously, you had to take care of NULL values when working with parameters or nullable columns. Even if you use non-nullable columns, NULL values can slip in when using a LEFT OUTER JOIN for example. So to make sure WHERE clauses or JOINS work like you intended to, you had to do some extra work for those pesky NULL values. But no more! Well, after you’ve upgraded to SQL Server 2022 at least 🙂
With IS NOT DISTINCT FROM, we can rewrite the SQL like this:
SELECT * FROM dbo.FactInternetSales WHERE OrderDate IS NOT DISTINCT FROM @orderdate;
Make a habit of writing your WHERE and JOIN clauses with this new predicate (or any Boolean comparison), it can save you some headaches.
You can find more info about this predicate and other new T-SQL stuff in this excellent blog post by Itzik Ben-Gan: Additional T-SQL Improvements in SQL Server 2022. And check out the official announcement of CTP 2.1 for more new features.
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