Sqlserver

This week I had a user come to me asking about how fields were defined on a few tables he was using in writing some reports. Long story short, he’s been tasked with writing some new reports and updating existing ones, but he doesn’t have visibility to the database itself so he’s left with the “ok, let’s try this” approach and then reading error messages to debug when things go sideways. Very tedious.

I’ve been a proponent of dbatools for close to a year now and even contributed to the project, but surprisingly haven’t been a heavy user of it. Mostly due to a lack of opportunity. I’m aware of many of the functions by virtue of working on the built-in documentation and following the project and presentations about it.

So when the need arose to move a development/test instance of SQL Server from a VM onto a physical server, I knew exactly what I wanted to do. I was warned that the contents of this instance had been moved once before and it resulted in over a week of work and a bunch of trouble. I can’t speculate on why this was as I wasn’t there to see it, but I wasn’t going to let that happen on my watch. So, with equal parts hubris and stubbornness (and a dash of naïveté), I dove in. We have the technology. We will migrate this thing.

One of the (many) fun things to do at PASS Summit is to check out the ribbons people have attached to their badges. Some are witty or goofy, others informational, others technical, and still more that let you express how you identify with a community within the community.

To celebrate dbatools and the awesome team & community around it, two limited edition badges will be available from/distributed by me and a handful of other folks all week at Summit. Check ’em out:

This month’s T-SQL Tuesday is hosted by Raul Gonzalez and he’s asked everyone to share things we might be a bit embarrassed about:

For this month, I want you peers to write about those important lessons that you learned the hard way, for instance something you did and put your systems down or maybe something you didn’t do and took your systems down. It can be also a bad decision you or someone else took back in the day and you’re still paying for it…

A few weeks ago I was looking at a query and got tripped up by the network and my own forgetfulness. It was a pretty simple query with a simple-looking execution plan. It didn’t even do that much work. About 20K logical reads and returned 200K records. For a server as large as the one I was working with, this should have been nothing. Instead, was waiting three minutes to get my results. My first thought was “aha, this query must need tuning, maybe a new index.”

For years I’ve looked at various queries online in sample code, diagnostic queries using DMVs, and the like and seen CROSS APPLY in the FROM clauses. But I’ve never really managed to comprehend what it was for or how it worked because I never saw a case where it was directly applied to something I was doing.

Finally, this week I had a breakthrough. I was working on updating a bunch of data but it was breaking on a small subset of that data. In this case, I was attempting to JOIN two tables on fields that should have been INTs, but in a very small number of cases one side was using a comma-delimited string. The user told me that someone else had done these updates in the past and didn’t encounter the problem I was having (so I knew that it was something i was doing “wrong”), but given that it was only a handful of broken updates she was OK with manually doing the updates (we were scripting it because we were updating potentially tens of thousands of records).

In a previous post, I expressed some frustration over Invoke-SqlCmd not setting an Application Name for its ODBC connection, leaving us with the generic .NET SqlClient Library when looking at active sessions in sp_who2 and sp_whoisactive (and any other monitoring tool). Unfortunately, I can’t really do anything about Invoke-SqlCmd aside from posting a suggestion on Connect or the Client Tools Trello board, but Invoke-SqlCmd2 has the same issue and that’s on GitHub. So, here we go!

Odds are, you’ve got more than one application or script accessing your database or SQL Server instance at any given time. You’re probably stacking them on a small number of servers in an attempt to cut down on licensing costs and resource usage. All those PowerShell scripts running on the central job server are running under a single service account, and you’ve got a lazy vendor who set up both the website and back-end application server to run under the same account, maybe even on a single app/web server.

Something in SQL Server that isn’t always obvious to beginners is that when you create a default value for a column on a table, SQL Server creates a constraint (much like a primary or foreign key). All constraints must have a name, and if one isn’t specified SQL Server will generate one for you. For example:

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CREATE TABLE [dbo].[point_types] (
   [typeid] [int] NOT NULL DEFAULT(NEXT VALUE FOR [pointtypeid])
  ,[typename] [nvarchar](30) NOT NULL DEFAULT 'Unspecified'
  ,CONSTRAINT [PK_PointType] PRIMARY KEY CLUSTERED ([typeid] ASC)
)

We’ve got a simple table here and both fields have a default value set (the primary key’s value is generated from a sequence object, pointtypeid). Time goes on, and a change in policy comes up which requires that I change the default value of typename to Unknown. To do this, I have to drop the constraint and re-create it. To find the name of the constraint, I can either ask sp_help, or run this query:

If you need to move data from one table into a new table, or even tables in a database into another database, the Import/Export Wizard in SQL Server Management Studio looks pretty tempting. Set up a source & destination, click a few buttons, kick back with a cup of tea and watch the progress bars, right?

It turns out that the wizard just isn’t as smart as it may seem. If you’re not careful, you won’t get what you’re expecting. Let’s check it out.