T-SQL on Andy M Mallon - AM²

T-SQL Tuesday: The last ticket I closed

Tue, 13 Feb 2024 12:41:20 -0500

For this month's T-SQL Tuesday, Brent Ozar (blog|Instagram) asks us to describe the most recent ticket we closed.

“We had a pretty significant wait spike…”

The literal last ticket I closed was “please run this script in production…”, and I don’t think it would be a very interesting blog post to talk about how I copy & pasted a query into SSMS, so let’s talk about a recent ticket instead, from the last couple of weeks.

Using OPENJSON, can't get results to GROUP BY

Sat, 24 Dec 2022 18:35:57 -0500

Question

I'm passing a JSON string to a stored procedure in order to insert warehouse inventory.

Sometimes, there will be multiple line items with the same product, going to the same shelf, on the same pallet (LPN), with the same date. I would like to aggregate those into one line in the table.

How do I prevent a trigger from firing for one process?

Tue, 08 Mar 2022 09:00:16 -0500

I recently saw a question on DBA Stack Exchange (it has since been deleted by the author), who had a “special process” that ran regularly, and as part of that process, they disabled the trigger, did some stuff, and re-enabled it. During that process, the step that disables the trigger would deadlock, and cause problems. So the asker was wondering how to catch & handle the deadlock during the DISABLE TRIGGER step.

Querying SERVERPROPERTY() and DATABASEPROPERTYEX() from a view (without knowing magic)

Fri, 17 Dec 2021 11:11:50 -0500

I’m not going to beat around the bush. I hate the SERVERPROPERTY() and DATABASEPROPERTYEX() system functions.

Loathing

The thing I hate the most about these two functions is that you need to know the right magic spells to make them work. Let’s look at SERVERPROPERTY() first. The syntax for the function is SERVERPROPERTY( ‘propertyname’ ), which is easy enough syntax, but the list of values for propertyname isn’t discoverable from SQL Server metadata, DMVs, or even IntelliSense. Instead, I need to check the docs for the list of allowable values. These property names are essentially magic words, and I need to check my spell book to make sure I get it right.

T-SQL Tuesday #143: My favorite short scripts

Tue, 12 Oct 2021 10:00:22 -0400

For this month's T-SQL Tuesday, John McCormack (blog) asks us: “What are your go-to short, handy scripts”? I've got so many handy dandy scripts, it was hard to choose.

Where to start?

I have so many go-to scripts that are short, amazing, and I use all the time. I’ve been using SQL Server since the turn of the century, and over the last two decades, I’ve found and written a lot of helpful things. And I have a terrible memory, so even if it’s just a few lines, I often keep it bookmarked or saved for when I need it. As an aside–remember that having a folder of utility scripts isn’t a sign of weakness or incompetence. If anything, it’s the opposite–those utility scripts are basically all battle scars for the database battles you’ve fought over your career. As we become senior, we just fine-tune our collection. With seniority, you don’t stop having that collection of scripts–you just get better at curating them, at making them generic & reusable.

What time is it in Oz?

Tue, 05 Oct 2021 15:54:03 -0400

There was a recent post on Database Administrators, where there was some confusion over Daylight Saving Time(DST) in Australian timezones. Let’s be honest though–timezones are confusing, especially when DST comes into play. Arizona Time doesn’t observe Daylight Saving Time, so sometimes it’s the same as Mountain Time, and sometimes it’s Pacific Time.

Stop using sp_hexadecimal & sp_help_revlogin

Tue, 06 Jul 2021 09:00:52 -0400

Since I started at Stack Overflow (read archived tweet) , I’ve had the chance to see some of the interesting challenges with running our databases at our scale.

My coworker Taryn Pratt (blog) recently blogged about fighting with deadlocks related to Stack Overflow for Teams.

Lots of logins

Taryn mentions in her post that each team gets their own login, user, schema, etc. This means we have a lot of logins. Additionally, we use Availability Groups for our High Availability, which means we need to keep those logins in sync across AG Replicas.

Find the SQL Server service account with sys.dm_server_services

Tue, 12 May 2020 09:00:56 -0400

SQL Server 2005 introduced Dynamic Management Views(DMVs). Technically, there are both views & functions–DMVs & DMFs, but colloquially they’re often simply referred to as just “DMVs”. DMVs simply return information about the state of the server or database and can be used for monitoring and troubleshooting of server/database health & performance.

Making non-SARGable queries seek, without changing the query

Wed, 06 May 2020 08:36:27 -0400

We’ve all been there. You’ve got a query where the JOIN or WHERE predicate is not SARGable. You’ve read about how this can be a problem, and how bad it is for performance.

Alas, you cannot change the query. Sometimes this reason is political, sometimes it’s because you’ve got a third-party app and simply don’t have access to the code. But you do have access to the database…

Fixing tempdb: Growing, shrinking, and removing data files

Tue, 21 Apr 2020 09:00:37 -0400

I recently came across a server where tempdb was breaking all the rules.

Data files were all different sizes. I want all data files to be the same size so that proportional fill uses them evenly.
There were 10 tempdb files, with 8 files on a dedicated disk, and 2 on a slower disk shared with other data files. And free space was sky high, so the extra files aren't needed anymore! (They were probably added to fix a short-term emergency, and never cleaned up.)
The log file was tiny, and didn't have room to grow. For a 500GB tempdb, the log file was only 4GB!

Three fixes

There are three problems I’ve got to fix. I need to (1) remove those two extra files, (2) grow the tempdb log file, and (3) even out the size of the data files (and shrink them a little to make room for the larger log file. We’re going to tackle these in the reverse order than I listed them–partially out of necessity, and partially because it’s going to be easier.

When STRING_SPLIT() falls short

Fri, 20 Mar 2020 10:00:54 -0400

This morning, my friend Aaron Bertrand (blog) posted a plea for help with STRING_SPLIT() improvements. I’m very much in Aaron’s corner on this, having written about the olden days myself.

Why `STRING_SPLIT()` is supposed to be awesome

CLR was fast, but inaccessible to many DBAs. XML was almost as good, but ugh, XML. And multi-statement table valued functions are evil but prevalent.

STRING_SPLIT() promised to be both super fast, and lift the code maintenance problem for DBAs who don’t know .NET and struggle with the crazy XML syntax.

Blocking with OBJECT_NAME()

Tue, 24 Dec 2019 10:38:36 -0500

As a DBA, you probably use the OBJECT_NAME() function quite a bit. I know I do. If you aren’t familiar with it, you can read the documentation if you want, but it’s a pretty straightforward function that converts object IDs into object names.

I ran into a scenario where one of my scripts in my stored procedures in my DBA Database was being blocked, and it turned out that using OBJECT_NAME() was the culprit.

Testing as another user...without their password

Wed, 18 Dec 2019 11:50:35 -0500

As a DBA or SQL Developer, you’ve surely encountered a scenario where something worked for you, but not for another user. DBAs usually are part of the sysadmin role, or have a collection of powerful permissions. If I run code as myself, I will never have permissions problems because my account is sysadmin. If I want to ensure permissions are correct, I need to run the code as the less-privileged account.

Changing a column from `int` to `bigint`, without downtime

Wed, 11 Dec 2019 08:00:41 -0500

Changing a column from int to bigint has gotten a lot easier since I started working on SQL Server back at the turn of the century. SQL Server 2016 introduced the ability to do ALTER TABLE...ALTER COLUMN as an online operation using the WITH (ONLINE=ON) syntax in Enterprise Edition. This wonderful syntax now allows you to alter a column from int to bigint without causing major blocking. The int to bigint conversion is one of the most popular data type changes I see–A developer inevitably creates the table thinking they will never have more than 2 billion rows… then some years or months later 2 billion becomes a reality.

How to create date buckets in T-SQL

Mon, 28 Oct 2019 10:00:47 -0400

I was fiddling around with some data, looking at making a quick aging report. I probably should have reached for Power BI Desktop, but sometimes I can be stubborn, and I wanted to get my T-SQL to work–if nothing else to figure out how to make it work.

Why does ALTER let me DROP?

Wed, 28 Aug 2019 09:00:19 -0400

I was recently chatting with a coworker, discussing why there is no discrete DROP permission for tables, procedures, etc. The conversation actually came from a #SQLHelp question on SQL Slack that was asked along the lines of “What if I want to let a user CREATE and ALTER objects, but not DROP them?”

Year 4: May 2017 - May 2018

Tue, 21 May 2019 08:30:21 -0400

In Year Three, I had a pretty big year. I kind of felt like I had peaked. I had received the Community Influencer of the Year Award and Microsoft MVP Award. Where do you go from there? Mostly, I just wanted to keep up what I was doing, and keep sharing what I was doing.

Code to purge data based on creation date

Thu, 04 Apr 2019 08:30:16 -0400

Yesterday, I talked about batching deletes, and the day before I talked about how much I like to delete data, and why it’s necessary to do it, despite being a data packrat.

Today, let’s look at just one scenario, and how I like to handle it. In my experience, this is one of the most common purge requirements (and probably the easiest), so first, let’s look at the business requirements.

Purging data with batched deletes

Wed, 03 Apr 2019 08:30:13 -0400

Yesterday, I wrote about the importance of planning your data purges. Today, let’s look at the simplest requirement for purging data: Keep data for X days after it’s created. There are tons of cases where this is the rule. Log data, telemetry data, even transactional data is often retained based on X days since it is created.

The thrill of purging old data

Tue, 02 Apr 2019 09:00:54 -0400

DBAs & Data professionals tend to be digital pack rats. My personal Google Drive is filled with random files that I refused to part with–even though it’s of questionable value. I lament that I do not have a copy of every paper I typed in high school or college–and I envy those who do. You never know when you’ll need notes from that meeting 6 years ago, or when you’ll need that funny GIF you created for an inside joke you no longer remember.

TSQL Tuesday #104: dbo.Check_FileSize

Mon, 09 Jul 2018 23:18:12 -0400

It’s T-SQL Tuesday, the blog party that SQL Server expert Adam Machanic (blog) started. This month’s episode is hosted by Bert Wagner (blog | vlog). The topic: Code You Would Hate To Live Without

It’s been a little bit since the last T-SQL Tuesday I joined, when I blogged about religion & politics (aka, Tabs vs Spaces). When I saw Bert’s excellent topic this month, I decided I’d try to get back on the horse again and do join the blog party again this month.

TSQL Tuesday #99: Tabs vs Spaces

Tue, 13 Feb 2018 07:02:30 -0500

It’s T-SQL Tuesday, the blog party that SQL Server expert Adam Machanic (blog) started. This month’s episode is hosted by Aaron Bertrand (blog). The topic: Dealer's Choice (Door Number 2: Bad Habits)

When I was a kid, Choose Your Own Adventure books were overwhelming because I wanted to explore every possible option–some things never change. This month for T-SQL Tuesday, Aaron offers two blogging options and I’ve chosen to do both. “Door Number 1” is a challenge to write about what you do in your free time, inspired by Drew Furgiuele’s #sqlibirum post. That blog post is over here. This post is for the “Door Number 2” option is to talk about his Bad Habits series–I’ve opted to bring up a topic Aaron hasn’t blogged about: tabs vs spaces.

TSQL Tuesday #99: SQL Tourism

Tue, 13 Feb 2018 07:00:45 -0500

It’s T-SQL Tuesday, the blog party that SQL Server expert Adam Machanic (blog) started. This month’s episode is hosted by Aaron Bertrand (blog). The topic: Dealer's Choice (Door Number 1: #sqlibrium)

When I was a kid, Choose Your Own Adventure books were overwhelming because I wanted to explore every possible option--some things never change. This month for T-SQL Tuesday, Aaron offers two blogging options and I've chosen to do both. "Door Number 1" is a challenge to write about what you do in your free time, inspired by Drew Furgiuele's #sqlibirum post. That blog post is below. My other post is for the "Door Number 2" option is to talk about his Bad Habits series--I've opted to bring up a topic Aaron hasn't blogged about: tabs vs spaces.

SQL Tourism? What’s that?

I made it the term, but it’s a very real thing. When I started travelling to speak at SQL Server events, I committed that I would make the most of it. To me, that means a lot more than just attending the event where I’m speaking. Sure, I want to learn and network at the event, but it means more than that, too. It means actually seeing the city where I’m speaking. It means enjoying the entire trip. It means making new friends, and connecting with old friends. Sometimes, it even means bringing my husband with me.

Parsing file names from paths using T-SQL

Wed, 17 Jan 2018 07:00:40 -0500

SQL Server is great at a lot of things. I spend a lot of time blogging about all the cool things that SQL Server does. But (you knew there was a “but”, didn’t you) SQL Server isn’t great at everything. Lets write about something that SQL Server is bad at.

Finding active transactions

Tue, 02 Jan 2018 09:04:07 -0500

Have you ever forgot to commit a transaction? Maybe you’ve even left for lunch and caused a problem while you were gone. Uncommitted transactions can cause all sorts of problems–not just blocking, but it can affect your Availability Groups & Mirroring, your TempDB version store if you’re using one of the snapshot isolation levels.

Finding the Leader Blocker

Thu, 26 Oct 2017 23:55:09 -0400

During the course of normal processing in a database, blocking happens. Blocking is “by design” because your database is on ACID. In an OLTP database, most of your transactions are short in duration, so we expect blocking to also be short in duration. If blocking occurs for a long time, this can cause problems.

Multi-Statement TVFs in Dynamics CRM

Tue, 22 Aug 2017 13:19:18 -0400

If you’re familiar with supporting the database behind Microsoft Dynamics CRM, you probably know that it’s not the fastest-performing database. Honestly, that shouldn’t be a surprise–it’s not designed to be a screaming-fast database. It’s designed to be a flexible database. Most Customer Relationship Management (CRM) systems are designed to be flexible so that they can meet the needs of many businesses in many industries with vastly different business requirements. They put those requirements ahead of database performance. That’s probably smart business, but I’m not a business person–I’m a database person. My experience with Dynamics CRM is when people come to me and say

What’s wrong with DELETE EXISTS?

Fri, 30 Jun 2017 14:26:41 -0400

This morning, when I logged into Twitter, the tweet at the top of my timeline was from Shane O’Neill (blog). It was to his blog post, Shane, What’s wrong with DELETE EXISTS?. It’s not that unusual that Shane would talk to himself in the third person, but I was intrigued by the title.

TSQL Tuesday #85: Backup + Recovery + ☁️

Tue, 13 Dec 2016 22:11:48 -0500

It’s T-SQL Tuesday, the blog party that SQL Server expert Adam Machanic (blog) started. This month’s episode is hosted by Kenneth Fisher (blog). The topic: Backup & Recovery

Your backups are my bread & butter

Backup & recovery are a DBA’s bread & butter. I always tell people that if you can’t restore from backup in an emergency, you should at least make sure your resume is up to date–you’ll need it. Part of my approach to making sure I have foolproof backups is making sure my setup is scripted and fool-proof to configure. Traditionally, this has been as simple as some T-SQL scripts that create the backup stored procedure, and create a few SQL Agent jobs.

T-SQL Tuesday #83: Roundup

Sun, 16 Oct 2016 20:49:50 -0400

For this month’s T-SQL Tuesday, I asked people to blog about the same old problems we’ve been dealing with for years. There were some great posts, including a batch of first-time contributors. You’ll notice some overlapping themes as you read through these responses–I think those themes represent some of the biggest, most important problems we have (like being able to restore backups). Thanks for everyone who contributed this month!

T-SQL Tuesday #83: We're still dealing with the same problems

Tue, 04 Oct 2016 09:00:37 -0400

What is T-SQL Tuesday?

T-SQL Tuesday is a monthly blog party hosted by a different blogger each month. This blog party was started by Adam Machanic (blog). You can take part by posting your own participating post that fits the topic of the month and follows the requirements below. Additionally, if you are interested in hosting a future T-SQL Tuesday, contact Adam Machanic on his blog.

Will a SELECT . . . INTO use short-circuit evaluation for a COALESCE?

Tue, 02 Aug 2016 14:45:55 -0400

Question

I'm building a stored proc that can take in two separate values that each can be used to identify a single record. One of these values may be null.

My logic is as follows: if IN_ORDER_ID is not NULL, save it to V_ORDER_ID. If it is NULL, then retrieve ORDER_ID with a query and save that to V_ORDER_ID. V_ORDER_ID is then used in the rest of the procedure.

T-SQL Tuesday #79 - COMPRESS()ing LOB data

Tue, 14 Jun 2016 09:00:25 -0400

It’s T-SQL Tuesday, the blog party that SQL Server expert Adam Machanic (blog) started. This month’s episode is hosted by Michael J Swart (blog). The topic: SQL Server 2016 is out!

SQL Server 2016 is hot off the presses, and Michael challenges us to blog about it.

I’ve been using SSMS 2016 (I’m impressed!), but I haven’t spent tons of time using the server-side bits. As I type this intro, the 2016 installer is chugging along getting a fresh instance ready for me to explore so I can write about…

Add-Equals operator

Tue, 24 May 2016 10:00:19 -0400

Shortcuts & tips from an Impatient DBA

This series of short posts will demonstrate some lesser-known features, keyboard shortcuts, and other tips that make my day as a DBA more productive. None of these are groundbreaking super-secret features–they are the little things that I do as part of my daily work that make me more efficient.

T-SQL Tuesday #78– sys.dm_db_file_space_usage

Tue, 10 May 2016 10:00:59 -0400

It’s T-SQL Tuesday, the blog party that SQL Server expert Adam Machanic (blog) started. This month’s episode is hosted by Wendy Pastrick (blog). The topic: Learn something new and blog about it

SQL Server 2016 is coming out next month, and it's chock full of new features that I can learn. Row-level security is interesting. Dynamic data masking sounds fun.

If you’re a regular reader of my blog, you probably know I try to approach questions from a unique angle. Instead of blogging about something cutting edge or sexy, I decided to scroll through the list of system views until I found one I didn’t recognize.

How to shrink a database in 4 easy steps

Thu, 28 Apr 2016 11:00:22 -0400

It’s a really common question: “How do I shrink my database?” Luckily, there’s also a really common answer: “Don’t.”

…but what if you really have to?

Perhaps you just implemented data compression, and have 60% free space in your database. Perhaps you just deleted a bunch of old data, and have significant free space in your database. There are a handful of scenarios where you have free space in the database, you’ll never use it, and you need to shrink. Just don’t make a habit of it.

CONVERT() to float using scientific notation

Wed, 20 Apr 2016 10:57:01 -0400

Someone posted to #sqlhelp on Twitter, asking the following: “Wondered if anyone could enlighten me as to why ISNUMERIC(‘7d8’) returns 1?”

Sure enough, SELECT ISNUMERIC('7d8') returns a 1.

WTF? d isn’t numeric!

OK, sure, if you say “seven-dee-eight” out loud it sounds like a number, but “d” is a letter, not a number.

T-SQL Tuesday #77– My favorite SQL Server feature

Tue, 12 Apr 2016 22:51:47 -0400

It’s T-SQL Tuesday, the blog party that SQL Server expert Adam Machanic (blog) started. This month’s episode is hosted by Jens Vestergaard (blog ). The topic: Favorite SQL Server Feature.

When I saw this topic, I was really excited. My mind started racing through all the awesome features in SQL Server. I spend a lot of time dealing with HA and DR--so many features to choose from...but are any of them my **favorite**? No, probably not. MSX and CMS have made my life so much easier, and they are incredibly cool, and I've not blogged about either of them...but...neither is my favorite.

Decoding sql_handle

Mon, 29 Feb 2016 10:05:54 -0500

If you’ve ever looked at sys.sysprocesses or sys.dm_exec_requests (or a number of other DMVs), you’ve noticed there is a column called “sql_handle” that contains some binary gobbledygook. Books Online gives the (un)helpful definition as “Hash map of the SQL text of the request.”

sp_WhoIsActive

In the context of currently-running processes, most people decode sql_handle with Adam Machanic’s (blog) sp_WhoIsActive. It’s really easy & straightforward–if you’re not familiar with Adam’s utility, download it and check it out. My friend Mike Kane (blog) has an interesting post on parameter combinations he regularly uses when using sp_WhoIsActive.

RECONFIGURE—When to use WITH OVERRIDE?

Tue, 17 Nov 2015 11:00:19 -0500

When you’re using sp_configure to change a system configuration, you have to run a RECONFIGURE to finalize your change. You even get the helpful output that reminds you to run RECONFIGURE:

Configuration option 'max degree of parallelism' changed from 0 to 1. 
Run the RECONFIGURE statement to install.

There are many places online with code samples (Books Online, blog posts, vendor documentation, etc) that actually use the additional “RECONFIGURE WITH OVERRIDE” syntax: Here. Here. Here. There are even posts that switch between including “WITH OVERRIDE” and not including it Here.

Converting delimited values to a table (efficiently?)

Tue, 21 Apr 2015 15:33:00 -0400

This is a pretty common problem. I think it’s a question every developer has asked at one time or another: “I want to pass in a comma-separated list of values, then convert it into a table."

Every company I’ve ever worked for has had a function that does this. Everyone does it differently. It’s never efficient. I’ve seen it done in CLR, I’ve seen it done as a multi-statement table-valued user-defined function (which we all know is the devil’s work). The CLR works, but it’s a black-box to the average DBA or SQL developer. The multi-statement TVF performs terribly, but has never been used heavily enough to make it to the top of my tuning list.

This morning, I saw Pinal Dave (blog) post on his blog about this topic, and he used a really elegant XML-based solution. It’s one of those solutions that’s so simple, it’s incredibly hard.

When I got to my desk this morning, I immediately wrapped Pinal’s code into a function that was backwards compatible to a multi-statement TVF version and performance tested them head-to-head.

Here’s my function definition:

sp_executesql with output parameters

Thu, 22 Jan 2015 20:05:00 -0500

One of my coworkers asked me about output parameters from dynamic SQL today. I pointed him at sp_executesql, which allows for passing parameters into or out of dynamic SQL. The syntax can be confusing at first blush (especially for a new DBA or developer), but it’s really pretty straightforward, easy, and useful.

T-SQL on Andy M Mallon - AM²

T-SQL Tuesday: The last ticket I closed

“We had a pretty significant wait spike…”

Using OPENJSON, can't get results to GROUP BY

Question

How do I prevent a trigger from firing for one process?

Querying SERVERPROPERTY() and DATABASEPROPERTYEX() from a view (without knowing magic)

Loathing

T-SQL Tuesday #143: My favorite short scripts

Where to start?

What time is it in Oz?

Stop using sp_hexadecimal & sp_help_revlogin

Lots of logins

Find the SQL Server service account with sys.dm_server_services

Making non-SARGable queries seek, without changing the query

Fixing tempdb: Growing, shrinking, and removing data files

Three fixes

When STRING_SPLIT() falls short

Why STRING_SPLIT() is supposed to be awesome

Blocking with OBJECT_NAME()

Testing as another user...without their password

Changing a column from `int` to `bigint`, without downtime

How to create date buckets in T-SQL

Why does ALTER let me DROP?

Year 4: May 2017 - May 2018

Code to purge data based on creation date

Purging data with batched deletes

The thrill of purging old data

TSQL Tuesday #104: dbo.Check_FileSize

TSQL Tuesday #99: Tabs vs Spaces

TSQL Tuesday #99: SQL Tourism

SQL Tourism? What’s that?

Parsing file names from paths using T-SQL

Finding active transactions

Finding the Leader Blocker

Multi-Statement TVFs in Dynamics CRM

What’s wrong with DELETE EXISTS?

TSQL Tuesday #85: Backup + Recovery + ☁️

Your backups are my bread & butter

T-SQL Tuesday #83: Roundup

T-SQL Tuesday #83: We're still dealing with the same problems

What is T-SQL Tuesday?

Will a SELECT . . . INTO use short-circuit evaluation for a COALESCE?

Question

T-SQL Tuesday #79 - COMPRESS()ing LOB data

Add-Equals operator

Shortcuts & tips from an Impatient DBA

T-SQL Tuesday #78– sys.dm_db_file_space_usage

How to shrink a database in 4 easy steps

…but what if you really have to?

CONVERT() to float using scientific notation

WTF? d isn’t numeric!

T-SQL Tuesday #77– My favorite SQL Server feature

Decoding sql_handle

sp_WhoIsActive

RECONFIGURE—When to use WITH OVERRIDE?

Converting delimited values to a table (efficiently?)

sp_executesql with output parameters

Why `STRING_SPLIT()` is supposed to be awesome