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Month: January 2016

Database Snapshots

Published 2016-01-26 by Kevin Feasel

Steve Jones explains database snapshots:

I’ve rarely dealt with database snapshots, outside of lab experimentation. They didn’t exist when I did most of my DBA work, and since then we haven’t seen the need for them at SQLServerCentral, though, I may suggest we add them to our deployment process since we can quickly roll back if something breaks.

However, I created one recently for a test and realized that I’d forgotten the syntax. Unlike the quick “create database xx” syntax I often use, with a snapshot I need to be more specific.

Word of warning:  don’t have more than one active snapshot of a single database.  If you do, you’ll likely have major performance problems.  My favorite use case for snapshots was building some semi-automated integration tests a few years back.  I created a tool for devs to create snapshots, and then they could run all the tests they wanted and revert the snapshot afterward.  There are some good uses in production environments as well.

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Reusable Powershell Scripts

Published 2016-01-26 by Kevin Feasel

Laerte Junior has an article on writing re-usable Powershell scripts:

There are the rules that I use in my day-to-day work in PowerShell. They’ve worked well for me over the years, but I’m not saying that they are carved in stone.

  • Learn the languageYou need to treat PowerShell as a serious .NET language. Like C#, F# or VB, it is impossible to know what the language can do, such as its features or commands without understanding the language and its paradigms? You can cut and splice other people’s scripts but you must have a good feel for the way that the language works before you can proceed any further

  • Use The HelpFor PowerShell, the help system is the first thing you must reach for: it must be your best friend. The designers of the language intended it to be well-used.

  • Use the  PowerShell CommunityThe PowerShell community is unique, because it has people who have come from a wide range of IT backgrounds. They bring their experience and wisdom with them. They will know more than you.  The combination of skills multiplies the speed at which the language develops. Read their posts, download their script and learn from them.

  •  Keep It Simple

  • Do not use Aliases, except for deliberate obfuscation.

  •  Write with considerationDo not try to cram all your scripted process into one line.  In the Shared and Corporate environment other people will maintain your code and will not necessarily have the same PowerShell knowledge as you. Be kind in your code.

After reading his article, check out Carlos Perez, et al’s Powershell Best Practices and Style Guide.

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Monitoring Deadlocks

Published 2016-01-26 by Kevin Feasel

Michael J. Swart has an Extended Event and a query to help monitor deadlocks:

Guess what? Apparently I “reinvented the wheel”. The extended events session I created is equivalent to one that Jeremiah Peschka wrote two years ago in Finding Blocked Processes and Deadlocks using SQL Server Extended Events. The embarrassing thing is that in Jeremiah’s article, he references a tool I wrote. And the first comment was written by yours truly.

There are a bunch of ways to capture deadlock information.  This is a good one.

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Named Constraints

Published 2016-01-26 by Kevin Feasel

Louis Davidson on naming constraints:

It has long been a habit that I name my constraints, and even if it wasn’t useful for database comparisons, it just helps me to see the database structure all that much eaiser. The fact that I as I get more experience writing SQL and about SQL, I have grown to habitually format my code a certain way makes it all the more interesting to me that I had never come across this scenario to not name constraints.

Temp tables are special.  There’s another reason to have non-named constraints on temp tables inside stored procedures:  it allows for temp table reuse, as shown on slide 21 in this Eddie Wuerch slide deck from SQL Saturday 75 (incidentally, the first SQL Saturday I ever attended).

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De-Duplicating Delimited Lists

Published 2016-01-25 by Kevin Feasel

Phil Factor looks at de-duplicating lists:

So there you have it. With XML tricks and window functions, we have more opportunity for kicking out any need for functions. To use this code, you’d just swap out the select statement that supplied my samples to the routine, for the lists that you want to deduplicate. Sure, this sort of job will never be quick because there are still correlated subqueries in there to upset the CPU! I am intrigued that there are such different ways of doing a solution for this task in SQL server. Are there yet other ways of doing it?

Cf. Aaron Bertrand’s tally table method.  Bonus points if you’re mentally screaming “CLR!”

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Azure Blob Storage Sync Updated

Published 2016-01-25 by Kevin Feasel

Randolph West reports on some bug fixes to Azure Blob Storage Sync:

During a SQL Server migration this month, I found some inconsistencies in my Azure Blob Storage Sync tool, so I made several improvements, and fixed an outstanding bug.

As you know, it relies on the naming convention provided in Ola Hallengren’s Maintenance Solution and comes in two parts: the AzureBlobStorageSync command-line application, and the AzureBlobStorageRestore command-line application.

Using Azure blob storage (or S3 if you go the Amazon way) as a long-term storage mechanism for database backups is a pretty smart idea.

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SSMSBoost

Published 2016-01-25 by Kevin Feasel

Allen McGuire talks about SSMSBoost:

Tip 4: Results Grid aggregates – Some people do a lot of calculations with their data, whether it’s sales data or whatever.  You end up saving the query results to Excel and about five minutes later you have the totals, etc.  With SSMSBoost, you can have your totals in seconds.  Below I’m selecting 10 records from a sales related table.  Say I want to get the SUM, MIN, MAX and Count of the SALEPRICE.  All I do is slide my mouse down the column highlighting the cells and a pop-up will appear with that information:

This is probably my second-favorite feature of SSMSBoost; my favorite is automated crash recovery, and my third-favorite its snippet support.  SSMSBoost has a free version and I use it myself.  I try not to push many tools here on Curated SQL, but this is one worth checking out.

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Starting SQL Server Without TempDB

Published 2016-01-25 by Kevin Feasel

Kenneth Fisher shows us how to start an instance in safe mode in case the drive hosting tempdb gets fried:

The situation: Your server is down. The drive/directory where tempdb is supposed to be doesn’t exist. Who knows why. Maybe those evil SAN guys forgot to re-attach your storage during a DR situation. You may or may not realize it but SQL Server will not start without tempdb. Which is fine. Just move it to a location that exists right? Well, yes. That is an important step. So here is how we

Move tempdb

I like the way Russ Thomas (and Kenneth Fisher) put it:  this is a low-occurrence, high-liability issue.

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Logins

Published 2016-01-25 by Kevin Feasel

Ed Leighton-Dick on logins:

The first concept to understand about SQL Server’s security model is the difference between authentication and authorization.

  • Authentication defines who is being given a right. SQL Server formally calls the authentication objects principals, but you’ll also see the older terms logins and users.

  • Authorization defines what rights are being given. Formally, these are called permissions. In modern versions of SQL Server, permissions are very granular and can be found on nearly every object in the instance. There’s also a vast hierarchy that interrelates all of the permissions. (We’ll cover permissions in a future post. For now, know that they’re there.)

Ed has started a series on security basics.  Given that there are relatively few people who talk security (and even fewer who know security), I consider this a great thing.

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