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
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
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
How difficult can it be to produce a simple hierarchical list in JSON, YAML, XML and HTML from a SQL Server table that represents a simple hierarchy within an organisation. Well once you know, it is easy and William Brewer is on a mission to tell you how … Read more
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
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
My new article about Graph Database Objects was just published, it’s really a very good new feature. Another new feature we have since SQL Server 2016 is R language. We can use R language inside the database to analyze our data. The possibility to use both technologies together is very interesting. Using graph objects we … Read more
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
Imagine you have some data. Maybe you’ve done a web redesign and you want to do some A/B testing to see if by redesigning the page your visitors spend more time reading your content. You set up an experiment in which visitors are randomly sent to either the old or new design, and you measure … Read more
SQL Server 2017 brings us some new T-SQL functions. They are very simple to use, and can also help us to simplify our T-SQL code. I’ll be talking about them in this article. String_AGG This new function solves an old and very interesting problem: How can we concatenate the contents of a column from several records in … Read more
The old system function IsNumeric() often causes exasperation to a developer who is unfamiliar with the quirks of Transact SQL. It seems to think a comma or a number with a 'D' in the midde of it is a number. Phil Factor explains that though IsNumeric has its bugs, it real vice is that it doesn't tell you which of the numeric datatypes the string parameter can be coerced into, and because it doesn't check for overflow. Phil comes to the rescue with a couple of useful alternatives, one of which works whatever version of SQL Server you have, and which tell you what datatype the string can be converted to.… Read more
Database code analysis will reduce the number of 'code smells' that creep into your database builds. It will alert the team to mistakes or omissions, such as missing indexes, that are likely to cause performance problems in production. It will allow the Governance and Operations team visibility into production readiness of the code, warning them of security loopholes and vulnerabilities. William Brewer describes the two technical approaches to database code analysis, static and dynamic, and suggests some tools that can help you get started.… Read more
It is possible to do a great deal with R within SQL Server, but it is best to start by doing analysis in R on numeric data from SQL Server and returning the results to SQL Server. There is great value to be gained even with this basic foundation. Robert Sheldon is on hand to give you a kick start with the first in his series on beginning with R in SQL Server.… Read more
User-Defined Functions (UDFs) are an essential part of the database developers' armoury. They are extraordinarily versatile, but just because you can even use scalar UDFs in WHERE clauses, computed columns and check constraints doesn't mean that you should. Multi-statement UDFs come at a cost and it is good to understand all the restrictions and potential drawbacks. Phil Factor gives an overview of User-defined functions: their virtues, vices and their syntax.… Read more
If the design of a relational database is wrong, no amount of clever DML SQL will make it work well. Dr. Codd’s Information Principle is that you have, inside the entity tables, the columns that model the attributes of that entity. The columns contain scalar values. Tables that model relationships can have attributes, but they must have references to entities in the schema. You split those attributes at your peril. Joe Celko explains the basics.… Read more
You can produce HTML from SQL because SQL Server has built-in support for outputting XML, and HTML is best understood as a slightly odd dialect of XML that imparts meaning to predefined tags. There are plenty of edge cases where an HTML structure is the most obvious way of communicating tables, lists and directories. Where data is hierarchical, it can make even more sense. William Brewer gives a simple introduction to a few HTML-output techniques.… Read more
Even though we're less inclined to print web-pages nowadays, it often makes sense to save useful content from a website as a PDF file to read offline. Dino Esposito explains printing from ASP.NET MVC. … Read more
SignalR is all about pushing notifications and data between web server and browser, but you can tap into a by-product of the work it has to do to keep track of the users who are currently online. This will provide a list of the users currently connected to a web community. SignalR has endpoints to push server events of any kind to the client, and thereby provides solutions for a number of common programming tasks.… Read more
One of the times that you need things to go right is when you are doing analysis and reporting. This is generally based on time and date. A sure-fire way of getting managers upset is to get the figures horribly wrong by messing up the way that you handle datetime values in SQL Server. In the interests of peace, harmony and a long career in BI, Robert Sheldon outlines some of the worst mistakes you can make when using SQL Server dates.… Read more
Although SQL Server supports XML well, XML's little cousin JSON gets no love. This is frustrating now that JSON is in so much demand. Maybe, Phil suggests, it is possible to leverage all that XML, and XPath, goodness in SQL Server to produce JSON in a versatile way from SQL Queries? Yes, it so happens that there are plenty of alternatives.… Read more
