SQL Server has a couple of different ways to represent hierarchies, but they do not allow storing any additional information that is important to the relationship between objects. In this article, Phil Factor explains how to use closure tables to overcome this deficiency.… Read more
Modifying data in Graph Database tables is similar to working with traditional tables, but there are several things to consider. Robert Sheldon explains how to insert, update, and delete rows of Graph Database tables and explains how to use several new helper functions. … Read more
Some time ago, Phil Factor wrote his booklet 'SQL Code Smells', collecting together a whole range of SQL Coding practices that could be considered to indicate the need for a review of the code. It was published as 119 code smells, even though there were 120 of them at the time. Phil Factor has continued to collect them and the current state of the art is reflected in this article. SQL Prompt is committed to cover as many as possible of them. Phil has also updated his book which you can download here.… Read more
Along with Graph Databases, Microsoft has introduced the new MATCH function for querying them. Robert Sheldon explains how to use the new function.… Read more
T-SQL does not have an easy way to transpose a row and a column. Of course, there is the PIVOT statement, but it doesn’t quite accomplish the task. In this article, Darko Martinovic shares another method using a SQLCLR stored prodedure.… Read more
SQL Server 2017 now includes a new feature to represent complex relationships in data called Graph Databases. Robert Sheldon introduces Graph Databases in the first article of this new series. … Read more
Stored procedures, for example, are very easy to document. The comment block at the beginning stays with the code and a CREATE or ALTER script contains everything to reproduce the proc. SQL Server tables, however, are more difficult to document. You can use Extended Properties to document columns and constraints, but working with Extended Properties is difficult at best. Phil Factor demonstrates ways to easily add Extended Properties to your build scripts. … Read more
Joe Celko reminisces about the origins of databases and one of the early pioneers, Charles Bachman. He explains how pointer chains were used to traverse data in the NDL standard and referential integrity that we use today.… Read more
There are several methods to pivot, or transpose, data in T-SQL, but most are difficult to understand and write. Phil Factor demonstrates how to take advantage of JSON support, introduced with SQL Server 2016, to create a function that makes pivoting data simple.… Read more
Writing aggregate queries is one of the most important tasks for anyone working with T-SQL. Determining the expressions required in the GROUP BY clause is not that difficult, but what do you do if you need to include different combinations of group by expressions in the same result set? Alfonso demonstrates how to use the GROUPING SETS operator to accomplish this task.… Read more
To support many applications, it makes sense for the database to work with JSON data, because it is the built-in way for a JavaScript or TypeScript application to represent object data. It can mean less network traffic, looser coupling, and less need for the application developer to require full access to the base tables of the database. However, it means that the database must do plenty of checks first before importing. Phil Factor explains how it can be easily done.… Read more
How do you record locations in SQL? Most relational database systems support spatial and geographical data, generally using the round-earth system based on the SQL specification of the Open Geospatial Consortium (OGC). However, this is not the only approach, as Joe Celko explains. … Read more
Over the years, Phil was struck by the problems of reading and writing JSON documents with SQL Server, and wrote several articles on ways of overcoming these problems. Now that SQL Server 2016 onwards has good JSON support, he thought that the articles would be forgotten. Not so, they continue to be popular, so he felt obliged to write about how you can use SQL Server's JSON support to speed the process up.… Read more
In the real world of business or scientific reporting and analysis, data can prove to be awkward. It can be plain wrong or it can be altogether missing. Sure, we have the NULL to signify unknown, but that doesn't play well with regular business reporting. There are a number of ways of dealing with missing information, and methods of estimating data from existing data has a long and respectable history. Joe Celko gets to grips with a data topic that is often treated with some trepidation. … Read more
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
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
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
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
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
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