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Category: T-SQL

Azure SQL DB String Concatenation and JSON Functions

Published 2024-12-16 by Kevin Feasel

Magda Bronowska takes a look at some functionality currently available only in Azure SQL Database and Managed Instance:

Microsoft releases the classic SQL Server every couple of years, with some functionality added through regular updates. On the other hand, the SQL Server offering in Azure (Azure SQL Database and Managed Instance) receives the latest features earlier.

This post highlights some of the T-SQL functions currently available in Azure SQL but not yet in classic SQL Server. However, with the recent announcement of SQL Server 2025, this might change next year. Keep in mind that some of these functions are in preview, so their behavior might evolve as they reach general availability.

Click through for those examples.

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Alternatives to Long IN() Lists in SQL Server

Published 2024-12-05 by Kevin Feasel

David Fowler still has a list:

This post comes off the back of my last, where I looked at issues caused by explicitly declaring a large number of values in an IN clause. The query processor ran out of internal resources and could not produce a query plan – When You’ve Managed to Confuse SQL With a Crazy IN Clause.

My suggestion was to put the values into a temp table and carry out a semi-join.

That got me thinking, which of the two methods would perform better.

I’m going to look at the two methods for different amounts of values and have a look at how they get on in terms of reads and total time.

Read on for the answer. If I’m surprised by anything in it, it’s that the threshold where temp tables out-perform the IN() clause is so high.

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New Syntax in SQL Server 2022

Published 2024-11-25 by Kevin Feasel

Steve Jones talks syntax:

At the recent 2024 PASS Data Community Summit, I saw a lightning talk from Mikey Bronowski on the New T-SQL Functions in SQL Server 2022.  Before the talk, I made a joke with him that none of these were new because it’s 2024. They’d been out for 2 years.

Mikey did a nice job, given that he only had 10 minutes, but it was enough to give attendees an idea of some new things they might investigate to use in their own code. If you missed the talk, or you don’t have access to the recordings, we have a series on SQL Server Central that covers these (Part 1, Part 2, Part 3) and helps you understand the new options. The list of language changes is also in the MS Docs under What’s New in the Language.

Steve asks about how much utilization there is of these. I think the problem is that so few organizations have adopted SQL Server 2022 that knowledge that these things even exist is quite low.

By the way, I do have a script covering many of these new bits of syntax as part of a talk on getting up to speed with core T-SQL changes since SQL Server 2012.

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The IS Operator in T-SQL

Published 2024-11-15 by Kevin Feasel

Eric Blinn wants to know of those NULLs:

Many data professionals search for help writing T-SQL queries containing columns with NULL values in a Microsoft SQL Server table. Some of the most common NULL functions include IS NULL, IS NOT NULL, NOT NULL, NULL, what is NULL, NULL vs NOT NULL, etc. In this SQL tutorial, the goal is to help you better understand how to work with NULL values in a SQL database.

Even the best of us have accidentally used = NULL in a script when we meant IS NULL. Which is totally different from ISNULL(), of course. And NULLIF(), naturally.

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Moving Averages in T-SQL

Published 2024-11-13 by Kevin Feasel

Jared Westover does the math:

Even though I enjoy using SQL Server, there are some things other tools do better. For example, calculating moving averages or rolling totals is often simpler in tools like Power BI or Excel. That’s because Microsoft built those programs with that functionality in mind. Recently, we had to optimize a complex moving average query written for SQL Server 2008R2. Surprise! There’s no built-in function for moving averages in SQL Server. But don’t worry; I’ll show you how to make it work.

Read on for the solution, as well as the mess we had to work with prior to SQL Server 2012.

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The Downside of UNISTR()

Published 2024-11-01 by Kevin Feasel

Solomon Rutzky shares some thoughts:

Since the new UNISTR function doesn’t provide new functionality, only convenience (“syntactic sugar” as some would say; see comment below), I would argue that it should not only use a more standard syntax, but also not waste the opportunity and provide more substantive convenience by handling several commonly used escape sequences. I suspect that the number of times people would use “\n” is several orders of magnitude more than the number of times people would inject emojis or other non-keyboard characters. Even better would be to incorporate common escape sequences into standard string parsing.

Read on for Solomon’s comment explaining why he is not a fan of UNISTR().

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T-SQL Notebooks in Microsoft Fabric

Published 2024-10-31 by Kevin Feasel

Dennes Torres tries out T-SQL notebooks:

T-SQL Notebooks is one of the new features announced during FabCon Europe.

The most distracted could miss the fact this is a new feature at all. Yes, it is. Notebooks were capable to support Spark SQL, but T-SQL is something new.

The main examples being announced are built with data warehouses, but let me confirm and highlight this:

T-SQL Notebooks support lakehouses as well.

There is at least one limitation: DML is not supported with lakehouses.

Saving my rant about lakehouses vs warehouses in Fabric, do read what Dennes has to say about T-SQL notebooks as they exist today.

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Query Processor Ran out of Internal Resources

Published 2024-10-31 by Kevin Feasel

David Fowler explains an error:

Recently I received a cry for help over Teams. The issue was that an application was throwing up the following SQL error,

The query processor ran out of internal resources and could not produce a query plan. This is a rare event and only expected for extremely complex queries or queries that reference a very large number of tables or partitions. Please simplify the query. If you believe you have received this message in error, contact Customer Support Services for more information.

I’ll be honest, that’s not one that I had seen before but it seemed pretty self explanatory. the query was just too complex for SQL to cope with. I asked what the query was, the answer was something similar to the snippet below,

Read on to learn what the problem was, as well as David’s answer. David had a simple rewrite retaining the IN clause, though you could also rewrite this with an INNER JOIN or even an EXISTS. One of those two alternative approaches might have a better performance profile, though there are no guarantees.

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Backing up SQL Server via T-SQL

Published 2024-10-23 by Kevin Feasel

I have a new video:

In this video, I show how to perform a variety of database backup operations via T-SQL, as well as how (and why) to back up to NUL and how to back up a database to a network share.

This one is not quite as lengthy as the prior video in the series: just 20 minutes instead of 30. That said, I do cover quite a bit of content around taking backups, something that every infrastructure DBA should be familiar doing.

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