25Jul 2022 by Grant Fritchey No Comments

Database Fundamentals #32: Create Unique Constraints with T-SQL

Database Fundamentals, SQL Server
In the last Database Fundamentals post, I explained what a unique constraint was and how you can create them using the GUI. Using TSQL to create a constraint is very similar to the primary key and foreign key constraints that you created in this post. You can use either the ALTER TABLE command or create the constraint when you make the table with the CREATE TABLE command. Using CREATE TABLE to Make a Unique Constraint There aren’t any new tables we need for this post, so we’ll create a table that we can drop immediately as soon as we’re done experimenting. You should already be familiar with the CREATE TABLE statement (or follow the link above): CREATE TABLE dbo.ConstraintTest ( TestName VARCHAR(50), CONSTRAINT UniqueName UNIQUE (TestName) ); This script creates…
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11Jul 2022 by Grant Fritchey No Comments

Extended Events for Anything But Query Tuning: xml_deadlock_report_filtered

SQL Server
One of my favorite little bits of information about Extended Events is the fact that everyone running a full instance of SQL Server has deadlock information available to them, even if they never enabled Trace Flag 1222 through the system_health session. That captures the xml_deadlock_report which has the full deadlock graph. However, what if you want to capture deadlock info, but, you're dealing the GDPR, and transmitting query values could be problematic? Enter xml_deadlock_report_filtered. xml_deadlock_report_filtered If you do a search for this event, you're not going to find much. Doesn't seem like anyone, including Microsoft, has bothered to document it. This is not going to be a comprehensive definition for all things xml_deadlock_report_filtered. However, I can show you why you might want to use it. This is a port of…
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05Jul 2022 by Grant Fritchey 2 Comments

Extended Events for Anything But Query Tuning: Unique Constraint Violations

SQL Server
Most of the time when I talk about or demo Extended Events, I spend more time talking about query tuning (I have a problem). However, there are tons of things that you can do with Extended Events. Here's a little one that came up, auditing unique constraint violations. Unique Constraint Violations Whether we're talking a primary key or just a constraint, the error you get is number 2627 when you attempt to add a non-unique value. So, the code for a simple way to track this in Extended Events would look like this: CREATE EVENT SESSION [UniqueConstraintViolation] ON SERVER ADD EVENT sqlserver.error_reported (WHERE ([error_number] = (2627))); That's it. That's all you need. Probably, it'd be a good idea to output this to a file (that's usually what I do). However,…
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11Apr 2022 by Grant Fritchey 7 Comments

Query Tuning and Easy Solutions

SQL Server
TLDR: There ain't one. I was privileged last week to be able to present a couple of sessions at the SQL Server and Azure SQL Conference (great event, I recommend it). One of my sessions was an intro to query tuning. Basically, I went through a bunch of common code smells and suggested different possible solutions. The one thing that came up, both from my own stories and the questions from the (engaged) audience, is just how much everyone wants a magic, run fast, switch. Query Tuning The Easy Way Here you go. The single easiest way to make your queries run faster: Just throw money at the problem. Buy more hardware. Buy bigger hardware. Get more disks and disk controllers (not just more disks). Go to the next highest…
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07Mar 2022 by Grant Fritchey 4 Comments

Query Plans in Azure Data Studio

SQL Server
I have long been a fan of Azure Data Studio, but one shortcoming has kept me from truly adopting it: Query Plans in Azure Data Studio. Sure, there was a plug-in you could install. Also, you could use a somewhat truncated version of Plan Explorer, but all I wanted was for SQL Server Management Studio plans to be query plans in Azure Data Studio. Go and get version 1.35 of the tool. Right now. DUDE! You have 1.35 of Azure Data Studio? Cool. Now, go to the menu bar. Click on "File." Click on "Preferences". Click on "Settings". Now, type the following into the search box: workbench editor enable preview. You should see this: Check the box below where it says "Workbench > Editor: Enable Preview" just like I have…
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28Feb 2022 by Grant Fritchey No Comments

Database Fundamentals #31: Unique Constraints from the GUI

Database Fundamentals, SQL Server
In the last few Fundamentals posts you were introduced to a couple of ways to limit and control the data stored in the tables in your database. A primary key won’t allow a duplicate value. A foreign key won’t allow a value to be added that doesn’t already exist in the parent table and it will prevent data from being deleted. These are types of constraints on data in your database. There are a bunch of other ways to constrain the data in an effort to ensure that the data stored is exactly what the business needs. The next few Fundamentals posts will cover several methods of limiting data. Unique Constraints to Stop Duplicates When the concept of the primary key was introduced earlier in the series, two different types…
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22Feb 2022 by Grant Fritchey No Comments

Azure Data Studio Intellisense

SQL Server
I recently saw a question about the Azure Data Studio Intellisense: "Why won't intellisense in Azure Data Studio work with different schemas?" Immediately I thought, "Wait, it does." But, testing is your buddy. Azure Data Studio Intellisense Azure Data Studio Intellisense is on by default. Also, I like it a little better than the one in SSMS because it will start trying to help you, as you type (like a 3rd party software I can't live without). However, they're partly right. Let's say I want 'Person.Address' so I start typing like this: It doesn't know that I have a table named 'Person.Address'. It's trying to be helpful. You can even see how it's doing a form of wild card search, suggesting that maybe 'db_accessadmin' is what I want since it…
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14Feb 2022 by Grant Fritchey No Comments

Extended Events Session Properties

SQL Server
I like Extended Events and I regularly use the Session Properties window to create and explore sessions. I'm in the window all the time, noting it's quirks & odd behaviors, even as it helps me get stuff done. However, found a new one. Let me tell you about just a few of them. Session Properties Window When you open the Extended Events session properties window for an existing session, in SSMS 18.1, it should look something like this: See the problem? Well, that is the problem. Here, look after I resize it: There it is. At the bottom. By default, the window isn't sized correctly so you see everything. In fact, I'm in the habit of maximizing the window, just because it makes it easier to work with. However, I…
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09Feb 2022 by Grant Fritchey 6 Comments

SQL Server, PostgreSQL and the Future

PostgreSQL, SQL Server
This is just a quick note to talk about the future, mine, yours and this blog. First, I'm not abandoning SQL Server. I'm actively working on a revision of the query performance tuning book (something I should be working on instead of writing this post). SQL Server is my first, and best, database love. We're not going anywhere, SQL Server and I. You can expect more posts on SQL Server, query tuning, execution plans, DevOps, community, #sqlfamily, and everything I've blogged about for the last, ooh, 14 years next month. Second, our family is growing. Just like when a family brings home a new baby, well, I'm adding another database. It doesn't mean I don't love my first database. I still do. We're just going to ALSO be talking about…
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07Feb 2022 by Grant Fritchey 1 Comment

Query Your Statistics: dm_db_stats_properties

SQL Server
We've always been able to look at statistics with DBCC SHOW_STATISTICS. You can even tell SHOW_STATISTICS to only give you the properties, STAT_HEADER, or histogram, HISTOGRAM. However, it's always come back in a format that you can't easily consume in T-SQL. From SQL Server 2012 to everything else, you can simply query sys.dm_db_stats_properties to get that same header information, but in a consumable fashion. dm_db_stats_properties You can pretty easily query the function dm_db_stats_properties: SELECT ddsp.object_id, ddsp.stats_id, ddsp.last_updated, ddsp.rows, ddsp.rows_sampled, ddsp.steps, ddsp.unfiltered_rows, ddsp.modification_counter, ddsp.persisted_sample_percent FROM sys.dm_db_stats_properties(OBJECT_ID('Production.Location'), 1) AS ddsp; You just have to pass in the object_id value and the stats_id value and you're off to the races. I can hear you. Why? So we can do things like this. What if I want to look at statistics that have fewer…
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