06Sep 2016 by Grant Fritchey 1 Comment

Query Store, Force Plan and “Better” Plans

SQL Server 2016, T-SQL
I am endlessly fascinated by how the Query Store works. I love teaching it at every opportunity too. Plus, almost every time I teach it, I get a new question about the behavior that makes me delve into the Query Store just a little bit more, enabling me to better understand how it works. I received just such a question at SQLSaturday Norway: If you are forcing a plan, and the physical structure changes such that a "better" plan is possible, what happens with plan forcing? Let's answer a different question first. What happens when the plan gets invalidated, when the index being used gets dropped or some other structural change occurs so that the plan is no longer valid? I answered that question in this blog post. The plan…
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29Aug 2016 by Grant Fritchey 7 Comments

Azure SQL Data Warehouse Execution Plans

Azure
Azure SQL Data Warehouse can sometimes feel like it's completely different from SQL Server, but under the covers, it is still (mostly) SQL Server and it does have execution plans. Let's take a look at one. I've created a new SQL Data Warehouse using the sample database available on the portal, AdventureWorksDW. Here's a query against that database: SELECT dd.FullDateAlternateKey AS OrderDate, dc.LastName, SUM(fis.SalesAmount) AS SumSalesAmount FROM dbo.FactInternetSales AS fis JOIN dbo.DimDate AS dd ON fis.OrderDateKey = dd.DateKey JOIN dbo.DimCustomer AS dc ON dc.CustomerKey = fis.CustomerKey GROUP BY dd.FullDateAlternateKey, dc.LastName HAVING SUM(fis.SalesAmount) > 5000.0 ORDER BY OrderDate DESC; If I attempt to capture an execution plan using the SQL Server Management Studio GUI, nothing happens. If I try to use T-SQL commands, I get an error that those commands are…
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25Aug 2016 by Grant Fritchey 4 Comments

PASS Board Update

PASS
Time for another update. The minutes for the June in-person meeting have been approved and are now ready for your information. We accomplished a lot in the two days and you can read what we did there. I'm pleased about two things. First, while it took until the July meeting to get the vote in, we have defined how the PASS board will deal with PASS-branded and PASS-sponsored events when it comes to payment to members of the Board. Thank you so very much for your feedback to my blog post on this topic. That feedback helped us to come to the conclusion that, for PASS-branded events (these are events that PASS doesn't run, like a SQLSaturday, but that are operating under the PASS brand) a board member can receive payment, say…
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22Aug 2016 by Grant Fritchey No Comments

Run For the PASS Board

PASS
When the word comes around for elections to the PASS Board, are you one of those people who, even in passing, considers running? If you are, my advice is to well, do it. By the way, here's that word. In order to make this a stronger, even more vibrant organization that continues to provide support to its members, we need more good leadership. A healthy set of choices, meaning lots of people, is necessary. That means we need you to run. There is no commitment required immediately. We've just started the process. What I'm asking you to do now, is start thinking about running, and thinking about it in a positive fashion. Track down a board member, or former board member, and find out what they think of the experience. You can…
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17Aug 2016 by Grant Fritchey 1 Comment

Updates to Azure Data Platform Learning Resources

Azure
I'm acting as the curator to a list of Azure Data Platform Learning Resources. It's speakers and teachers, blogs, articles and more, all focused around the Azure Data Platform. I have it hosted on GitHub so that anyone can contribute. There have been several updates recently that you may want to take a look at. If you're looking for where and how to get started in the Azure Data Platform, this is a great resource to get you going. If you're teaching the Azure Data Platform, anything from PowerBI to DocumentDB to Azure SQL Data Warehouse and all the stuff in between, please add your information so that this list is up to date.
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15Aug 2016 by Grant Fritchey 5 Comments

Query Store, Force Plan and Dropped Objects

Azure, SQL Server 2016
I love the Query Store. Seriously. It’s a huge leap forward in the capabilities of Azure SQL Database and SQL Server in support of performance monitoring and query optimization. One of my favorite aspects of the Query Store is the ability to force plans. Frankly though, it’s also the scariest part of the Query Store. I do believe that plan forcing will be one of the most ill-used functions in SQL Server since the multi-statement table-valued user-defined function (don’t get me started). However, unlike the UDF, this ill-use will be because of poor understanding on the part of the user, not a fundamental design issue. No, plan forcing and the Query Store are very well constructed. Let me give you an example of just how well constructed they are. Let’s…
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09Aug 2016 by Grant Fritchey 4 Comments

Azure SQL Database For Your First Database

Azure
This is post 8 supporting  Tim Ford’s (b|t) initiative on #iwanttohelp, #entrylevel. Read about it here. In post #6, I talked about Azure SQL Database as one of the choices you have when you're picking the type of SQL Server instance you want to run. I want to expand on why you should be considering moving into Azure SQL Database at the start of your career and some of the important differences you'll have to be aware of as you get going. Since you are right at the start of your career, you may as well plan on maximizing the life of the knowledge and skills you're building. By this, I mean spend your time learning the newest and most advanced software rather than the old approach. Is there still work for people who only know…
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01Aug 2016 by Grant Fritchey 1 Comment

There Is No Difference Between Table Variables, Temporary Tables and Common Table Expressions

SQL Server, SQL Server 2016, SQL Server 2017, T-SQL
I actually saw the above statement posted online. The person making the claim further stated that choosing between these three constructs was "personal preference" and didn't change at all the way SQL Server would choose to deal with them in a query. Let's immediately say, right up front, the title is wrong. Yes, there are very distinct differences between these three constructs. Yes, SQL Server will absolutely deal with these three constructs in different ways. No, picking which one is correct in a given situation is not about personal preference, but rather about the differences in behavior between the three. To illustrate just a few of the differences between these three constructs, I'll use variations of this query: SELECT * FROM Sales.Orders AS o JOIN Sales.OrderLines AS ol ON ol.OrderID = o.OrderID WHERE ol.StockItemID = 227; The…
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25Jul 2016 by Grant Fritchey 2 Comments

Monitor Query Performance

Azure, SQL Server, SQL Server 2016
Blog post #7 in support of Tim Ford’s (b|t) #iwanttohelp, #entrylevel. Read about it here. Sooner or later when you're working with SQL Server, someone is going to complain that the server is slow. I already pointed out the first place you should look when this comes up. But what if they're more precise? What if, you know, or at least suspect, you have a problem with a query? How do you get information about how queries are behaving in SQL Server? Choices For Query Metrics It's not enough to know that you have a slow query or queries. You need to know exactly how slow they are. You must measure. You need to know how long they take to run and you need to know how many resources are…
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18Jul 2016 by Grant Fritchey 14 Comments

Common Table Expression, Just a Name

SQL Server, SQL Server 2016, T-SQL
The Common Table Expression (CTE) is a great tool in T-SQL. The CTE provides a mechanism to define a query that can be easily reused over and over within another query. The CTE also provides a mechanism for recursion which, though a little dangerous and overused, is extremely handy for certain types of queries. However, the CTE has a very unfortunate name. Over and over I've had to walk people back from the "Table" in Common Table Expression. The CTE is just a query. It's not a table. It's not providing a temporary storage space like a table variable or a temporary table. It's just a query. Think of it more like a temporary view, which is also just a query. Every time I explain this, there are people who don't…
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