Calculated Dimensions

Ginger Grant shows how calculated dimensions can solve the classic role-playing dimension problem in Analysis Services Tabular:

Working with role playing dimensions, which are found when you have say multiple dates in a table and you want to relate them back to a single date table, have always been problematic in SQL Server Analysis Services Tabular. Tabular models only allow one active relationship to a single column at a time. The picture on the left shows how tabular models represent a role playing dimension, and the model on the right is the recommended method for how to model the relationships in Analysis Services Tabular as then users can filter the data on a number of different date tables.

The big downside to this is one has to import the date table into the model multiple times, meaning the same data is imported again and again. At least that was the case until SQL Server 2016 was released. This weeks TSQL topic Fixing Old Problems with Shiny New Toys is really good reason to describe a better way of handling this problem.

Read on for how to implement calculated dimensions.

Not All Shiny Toys Are Good

Wayne Sheffield rains on our parade:

There are other issues with the MERGE statement. It has bugs… some of which can cause database corruption.

Here we have a Shiny New Toy (feature), supposed to make life easier, yet it causes problems. Until it can perform better (and the bugs are eliminated), I just don’t use it.

Beware the Shiny New Toys.

Wayne makes a great point.  Not all new things are good, even when they’re potentially quite useful.  I love shiny new toys a lot, but part of being a database administrator is protecting data, and part of that means being able to trust your tools.  Sometimes the tools work really well right out of the gate, and sometimes (like in the case of MERGE) they don’t.

Single-Query Wait Stats

Robert Davis shows off a new wait stats-related feature in 2016 SP1:

Paul’s process gives you info on every instance of a wait the query experienced and it’s very easy to aggregate those results to see the top waits and their total effect on a query. Quite often though, you don’t need a lot of detail. You don’t need to know every wait, just the top several. If you are already generating the actual query plan to have a in-depth look at the plan, wouldn’t it be nice if the query wait stats were already in there for you?

Now they are. In SQL Server 2016 (I’m told it came in SP1, but I don’t have a non-SP1 instance to verify that), the actual execution plan includes the top waits for the query execution in the plan. You can see them by clicking on the left-most (first) operator in the plan and viewing the Properties (shortcut F4). It will list the top waits right there in the properties dialog for you.

Getting single-query wait stats in the execution plan makes life so much simpler.

Server-Level Database Permissions

Kenneth Fisher shows off some special server-level permissions:

So what’s our shiny new permissions toy? Well, over time we have been getting more and more server level permissions that affect database level objects. A lot of these can be really useful and I’m hoping we will see more and more of them.

Click through for a couple helpful tables of permissions.

Change Detection Temporal Tables

Adam Machanic shows how to find net changes using temporal tables:

For now, consider the following set of propositions, given that we’re asking at time Y for all changes since a prior time X.

  • INSERT: The key did not exist at time X but does exist at time Y.
  • DELETE: The key existed at time X but does not exist at time Y.
  • UPDATE: The key existed at both time X and at time Y, and at least one change occurred between time X and time Y.

Given these assumptions, we can begin work on a temporal queries that return the necessary rows. Solving for these conditions will require all rows that were active as of time X, rows that were (or are) active at time Y, and for the final case, all rows that were active in-between times X and Y. Since this is a range-based scenario, our best Temporal predication option will be either FROM or BETWEEN. The difference between these two is subtle: FROM uses an open interval (non-inclusive at both endpoints), whereas BETWEEN uses a half-open interval, inclusive on the end date. Given the choice in the scenario, BETWEEN makes more sense, as we can take advantage of the inclusive endpoint to avoid dropping a badly-timed row. But more on that in a moment.

Adam put a lot of thought into edge cases, making this a must-read.

Metaphones In SQL

Phil Factor builds a function to generate metaphones in SQL Server:

Metaphone algorithms are designed to produce an approximate phonetic representation, in ASCII, of regular “dictionary” words and names in English and some Latin-based languages. It is intended for indexing words by their English pronunciation. It is one of the more popular of the phonetic algorithms and was published by Lawrence Philips in 1990. A Metaphone is up to ten characters in length.

It is used for fuzzy searches for records where each string to be searched has an index with a Metaphone key. You search for all records with the same or similar metaphone key and then refine the search by some ranking algorithm such as Damerau–Levenshtein distance. Metaphone searches are particularly popular with ‘ancestor’ sites that search on surnames where spellings vary considerably for the same surname. The current version, Metaphone 3, is actively maintained by Lawrence Philips, developed to account for all spelling variations commonly found in English words, first and last names found in the United States and Europe, and non-English words whose native pronunciations are familiar to English-speakers. The source of Metaphone 3 is proprietary, and Lawrence charges a fee to supply the source.

Read on for the script.

Using ostress

Erik Darling explains how to stress test using ostress:

You can spend a lot of money on people and complicated software to design, run, and monitor workloads against test environments, or you can throw together tests with some free tools like SQL Query Stress or Microsoft’s RML Utilities.

RML Utilities is pretty cool, and includes ostress.exe along with some other components. What I really like about ostress is that it’s all CLI, so you can call it from Agent Jobs, and feed it all sorts of cool options. When you create the Agent Job, you just use the Operating system (CmdExec) type of step instead of T-SQL, or whatever else.

For simulated load, ostress is powerful.  For “ripped from the headlines” load, the Database Experimentation Assistant might do the trick once it matures.

Generating SQL Permutations

Kevin Feasel

2017-02-15

T-SQL

Michael J. Swart uses a recursive common table expression and bit shifting to build a full set of permutations:

If you google “generating permutations using SQL”, you get thousands of hits. It’s an interesting problem if not very useful.
I wrote a solution recently and thought I’d share it. If you’re keen, try tackling it yourself before moving on.

Click through for the script.  It’s an interesting approach and might be worth playing a round of code golf.

Managing Azure SQL Database Firewall Rules

Cedric Charlier shows how to manage Azure SQL Database firewall rules from within Management Studio:

When you create a new Azure database, you usually need to open the firewall to remotely administrate or query this database with SSMS. An option is to create rules from the Azure Portal. It’s surely a convenient way to do it when you create a database but I prefer to keep a minimum of tools and when the Azure portal is not open, I prefer to not have to open it just to define a few firewall rules.

Opening the firewall with SSMS is a kind of chicken and eggs problem: to connect to your database/server, you need to open the firewall. Hopefully, SSMS has a great suite of screens to call the underlying API of Azure Portal and open the firewall for the computer running SSMS.

Cedric shows off sp_delete_firewall_rule but there’s also a corresponding sp_set_firewall_rule.

Maintenance Plan Updates

Kevin Hill looks at maintenance plan updates in SQL Server 2016:

True to my typical post style which focuses on small shops, accidental DBAs, and junior DBAs I went looking for something that could very easily benefit people that are using the basic SQL Server features.  In this case they may not even realize how limited they were.

I chose to write about Index Maintenance in the built-in Maintenance Plan portion of SQL Server.

A brief summary of the built-in Maintenance Plans is that they allow you to drag-and-drop your way to basic SQL Server maintenance items such as Backups, Index maintenance, CheckDB, Statistics updating, etc.  This a tool that has been around since at least version 7 that I know of.  It wasn’t always very good, and it gets a bad rap from a lot of DBAs.  It has been dramatically improved over the years in flexibility and reliability.

Read on for the changes.  I’m really not a fan of maintenance plans, but if they’re going to exist, they should at least be as good as possible.

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