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Simple SQL: Random Thoughts

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How does one get a truly random sample of data of a certain size from a SQL Server database table. Well, there are simple non-portable tricks one can use, such as the NewID() function, but then refining those can be tricky. Take the Rand() function for a start. Can it really provide you with a truly random number? Why doesn't the TABLESAMPLE clause give you a set number of rows? Joe Celko scratches his head a bit, explains some of the issues and invites some suggestions and tricks from readers.… Read more

SQL Server R Services: Working with ggplot2 Statistical Graphics

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It is when you use R in SQL Server with one of the huge range of packages that comes with it that you can begin to appreciate the power of the system. With a package such as ggplot there are many 'knobs one can twiddle' in order to get spectacular and informative visualisations. Rob Sheldon continues his beginners series for R in SQL Server by showing how to refine the output to get it as you need it.… Read more

The Power of Python and SQL Server 2017

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Python is new to SQL Server 2017. It is intended primarily to allow the use of Python-based machine-learning within SQL Server, but it can be used for far more than this, with any Python libraries or Frameworks. To provide an example of what is possible, Hitendra shows how to use the feature securely to provide intelligent application caching, where SQL Server can automatically indicate when data changes to trigger a cache refresh. … Read more

Statistics in SQL: Student’s t-test

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Many undergraduates have misunderstood the name 'Students' in the t-test to imply that it was designed as a simple test suitable for students. In fact it was William Sealy Gosset, an Englishman publishing under the pseudonym Student, who developed the t-test and t distribution in 1908, as a way of making confident predictions from small sample sizes of normally-distributed variables. As Gosset's employer was Guinness, the brewer, Phil Factor takes a sober view of calculating it in SQL.… Read more

Automated Database Provisioning for Development and Testing

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If your development team needs to work on anonymised copies of the current production database, and if changes are being delivered rapidly as well, that could mean a lot of time and routine DevOps work copying databases. SQL Clone was designed for tasks like this. Grant Fritchey investigates whether you save time, effort and scripting over the more traditional approach, and at what point it makes sense to use it.… Read more

Pseudonymization and the Inference Attack

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It is surprising that so much can be identified by deduction from data. You may assume that you can safely distribute partially masked data for reporting, development or testing when the original data contains personal information. Without this sort of information, much medical or scientific research would be vastly more difficult. However, the more useful the data is, the easier it is to mount an inference attack on it to identify personal information. Phil Factor explains.… Read more

Using SQL Server Query Hints with Entity Framework

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Entity Framework (EF) is designed to work with a variety of data sources. Although this presents many advantages, there is a downside that many of the special features of a data source such as SQL Server are off-limits. Query Hints are an example: though often misused, they are occasionally important. Dennes Torres shows how you can use these in EF, using a command interceptor that will allow you to use any query hint with SQL Server.… Read more

The Basics of Good T-SQL Coding Style – Part 4: Performance

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There are several obvious problems with poor SQL Coding habits. It can make code difficult to maintain, or can confuse your team colleagues. It can make refactoring a chore or make testing difficult. The most serious problem is poor performance. You can write SQL that looks beautiful but performs sluggishly, or interferes with other threads. A busy database developer adopts good habits so as to avoid staring at execution plans. Rob Sheldon gives some examples.… Read more

Data in Motion and Data at Rest

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Microsoft (StreamInsight), and Azure Stream Analytics represent a very different model for processing data. They are concerned with processing complex event streams of data (CEPs) from such things as sensors to deduce significant patterns and apply filters. Joe Celko discusses the background to an intriguing technology of complex event processing to establish the difference between data at rest, and data on the move.… Read more

SQLCLR in Practice: Creating a Better Way of Sending Email from SQL Server

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SQLCLR is now considered a robust solution to the few niche requirements that can't be met by the built-in features of SQL Server. Amongst the legitimate reasons for avoiding SQLCLR, there is the fear of getting bogged down in code with special requirements that is difficult to debug. Darko takes a real example, extending the features of sp_send_dbmail, to demonstrate that there need be few terrors in SQLCLR. … Read more

The Best of Both Worlds: Using Excel and Power BI Together

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Excel and Power BI work well together. This allows you to use the two tools together to provide for many types of business workflow and BI practices. You can publish an Excel file to Power BI to share with others, analyse a Power BI dataset in Excel or import either an Excel workbook or Excel data to Power BI. You can gain the workgroup power and business-orientation of Power BI without losing the ease and versatility of Excel. Saurabh shows how.… Read more

Investigating the Cause of SQL Server High CPU Load Conditions When They Happen

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Any DBA who is trying to find the cause of an intermittent problem with a server or database dreams of being able to use a query or procedure take a snap of the relevant variables at the point when the problem occurred. Laerte takes an example of a slow-running query hogging resources to show that you can run queries when a WMI alert is fired, and save the results for later inspection, whenever it happens.… Read more

SQL Server R Services: Digging into the R Language

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It is not just the analytic power of R that you get from using SQL Server R Services, but also the great range of packages that can be run in R that provide a daunting range of graphing and plotting facilities. Robert Sheldon shows how you can take data held in SQL Server and, via SQL Server R Services, use an R package called ggPlot that offers a powerful graphics language for creating elegant and complex plots.… Read more

SQL Data Aggregation Aggravation

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When we have to deal with and store a lot of data, it makes sense to aggregate it so that we store only the information we actually need. If we get this right, this works well, but the design of the system takes care and thought because the problems can be subtle and various. Joe Celko describes some of the ways that things can go wrong and end up providing incorrect, inaccurate or misleading results.… Read more

SQL Graph Objects in SQL Server 2017: the Good and the Bad

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Graph databases are useful for certain types of database tasks that involve representing and traversing complex relationships between entities. These can be difficult to do in relational databases and even trickier to report on. Until now, we have had the choice of doing it awkwardly in SQL Server or having an ancillary database to tackle this type of task. SQL Server 2017 will be bringing graph capabilities to the product but will these features prove to be good enough to allow us to dispense with specialised Graph databases? Dennes Torres decided to find out.… Read more

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