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Curated SQL Posts

Databases In Source Control

Published 2017-01-16 by Kevin Feasel

Robert Sheldon walks through core concepts of source control:

The source control system can’t merge the two file versions until Barb resolves the conflict between black bear and brown bear (the additions of wolf and fox still cause no problem).

When conflicts of this nature arise, someone must examine the comparison and determine which version of bear should win out. In this case, Barb decides to go with black bear.

It’s worth considering the risk associated with this merge process. Barb’s commit fails, so she can’t save her changes to the repository until she can successfully perform a merge. If something goes wrong with the merge operation, she risks losing her changes entirely. This might be a minor problem for small textual changes like these, but a big problem if she’s trying to merge in substantial and complex changes to application logic. This is why the source control mantra is: commit small changes often.

The article is more of an intro to source control, but if you aren’t familiar with how source control works, it’s a great read.  Regardless, the best thing you can do for yourself is to get your database code in source control.  That opens up the possibility for safer refactoring of code.

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CRISP-DM

Published 2017-01-16 by Kevin Feasel

Steph Locke explains the CRISP-DM model for data mining projects and applies it to data science projects:

Within a given project, we know that at the beginning of our first ever project we may not have a lot of domain knowledge, or there might be problems with the data or the model might not be valuable enough to put into production. These things happen, and the really nice thing about the CRISP-DM model is it allows for us to do that. It’s not a single linear path from project kick-off to deployment. It helps you remember not to beat yourself up over having to go back a step. It also equips you with something upfront to explain to managers that sometimes you will need to bounce between some phases, and that’s ok.

This is another place in which “iterate, iterate, iterate” ends up being the best answer available.

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More On Columnstore Batch Mode

Published 2017-01-16 by Kevin Feasel

Sunil Agarwal talks about batch mode processing with columnstore indexes:

While these results may not appear as dramatic on my laptop, the picture below shows the performance gains with Window Aggregates on a Server class machine with large DW database. The orange bar represents the query speed up we got with Window Aggregate operator in BatchMode. The highest speed up we saw was 289x!!

Batch mode is generally a huge benefit for data warehousing environments.

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Getting Effective Permissions

Published 2017-01-13 by Kevin Feasel

Jana Sattainathan explains how to get a user’s effective permissions:

Microsoft has provided a function named fn_my_permissions that gets the permissions for you. It has multiple classes of objects for which you can get permissions. We already know about SERVER, DATABASE and OBJECT but there are a lot more. To get that list of classes, let us use fn_builtin_permissions function

The one thing I wish this function did was let a sysadmin see another user’s effective permissions without using EXECUTE AS; I’d like to be able to apply that function to sys.logins and get an exploded list for reporting.

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Upgrading SSRS From 2008R2 To 2014

Published 2017-01-13 by Kevin Feasel

Dave Turpin needed to perform an upgrade of a Reporting Services installation:

So let me share with you my biggest take away from this project:  EVERYTHING ABOUT USER CREATED REPORTS IS STORED IN THE SQL Server Reporting databases.  So if you are reading this post you probably are about to move an instance of SSRS, and may be concerned about the many, many reports involved.

Based on my one experience with this, there is need to move individual reports.  If you follow the process carefully, all of the existing reports will be re-created on the new machine.  It’s not quite magic, but it sure feels like it when everything shows up on the new system.

Read on for the solution Dave came up with.

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Basics Of Azure Analysis Services Management

Published 2017-01-13 by Kevin Feasel

Bill Anton walks through some of the basics of managing an Azure Analysis Services cube:

The quickest win – from an ROI perspective – for Azure AS is the ability to pause the instance during extended periods of inactivity – for example, at night, when there aren’t any users running reports.

This can be achieved via the Suspend-AzureRmAnalysisServicesServer cmdlet we saw in the previous post.

Read on for a few tips of this ilk, including resizing the server.

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Joins Galore

Published 2017-01-13 by Kevin Feasel

Lukas Eder has a comprehensive guide to joining data using SQL:

Alternative syntaxes: NATURAL JOIN

An more extreme and much less useful form of "EQUI" JOIN is the NATURAL JOIN clause. The previous example could be further “improved” by replacing USING by NATURAL JOIN like this:

SELECT *
FROM actor
NATURAL JOIN film_actor
NATURAL JOIN film

Notice how we no longer need to specify any JOIN criteria, because a NATURAL JOIN will automatically take all the columns that share the same name from both tables that it joins and place them in a “hidden” USING clause. As we’ve seen before, as primary keys and foreign keys have the same column name, this appears quite useful.

There is a high likelihood that you will learn at least one new thing here; for example, check out lateral joins (which SQL Server practitioners know as something else).

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Turning On SQL Authentication

Published 2017-01-13 by Kevin Feasel

Kenneth Fisher hits a frequent cause of login failure:

No go. Next thing to check is the password. The error I’m getting does indicate the incorrect password so it’s a distinct possibility. Now when I moved the server principal I made sure to copy the password hash from the old server so the password should be the same. However, I’ve made mistakes before, and odd things happen, so I decided to change the password just in case. Before I did I backed up the original password just in case.

The solution is something that I’ve seen a lot of sysadmins forget to do in their setup processes.

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DDL And The Optimizer

Published 2017-01-12 by Kevin Feasel

Grant Fritchey notes that data definition language (DDL) queries do not appear to go through the query optimizer:

We can check whether or not you’re going to get an execution plan for this in two easy ways. You can capture the estimated plan, or run the query and capture the actual plan. Since most of the time, it’s preferable to work with the added runtime information that an actual plan provides, let’s start there. However, if you execute the query above and try to capture an actual plan, you will not get one. So, let’s capture the estimated plan instead. Here’s what we see:

Not much of a plan really.

Read on for that, and start holding your breath for a new execution plans book.

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