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Statistics in SQL: Student’s t-test

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.

2017-10-12

3,767 reads

External Article

Network Configuration of SQL Server Always On Availability Groups in Azure

Implementing SQL Server Failover Clustering in Azure virtual machines differs in several aspects from its on-premises implementations. These differences reflect some of the unique characteristics of the storage and network infrastructure services in the Microsoft cloud environment. In this article, Marcin Policht looks at the networking aspects of clustered deployments of SQL Server 2016 in Azure.

2017-10-11

2,735 reads

External Article

Automated Database Provisioning for Development and Testing

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.

2017-10-10

4,465 reads

External Article

SQL Server Integration Services SSIS 2016 Tutorial

SQL Server Integration Services (SSIS) is the integration and ETL (extract – transform – load) tool in the Microsoft Data Platform stack. SSIS is typically used in data warehousing scenarios, but can also be used in common data integration use cases or just to move data around. SSIS is used behind the scenes in the Maintenance Plans of SQL Server and in the Import/Export wizard.

2017-10-06

4,301 reads

External Article

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

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.

2017-10-05

6,056 reads

External Article

Data in Motion and Data at Rest

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.

2017-10-03

3,971 reads

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Question of the Day

Getting the Average

I have this data in the dbo.Commission table in a SQL Server 2022 database. 

salesperson commission
Brian       12
Brian       16
Andy        7
Andy        14
Andy        21
Steve       20
Steve       NULL
All the data is a varchar, and I decide to run this query to get the totals for each salesperson. 
SELECT SalesPerson
     , AVG(TRY_PARSE(Commission AS int)) AS TotalCommission
 FROM commission
 GROUP BY SalesPerson
GO
What average commission is calculated for Steve?

See possible answers