Tables that return the value of the data in the table at a particular point of time have been with us since the first relational database, but have always required special queries and constraints, and can be tricky to get right. System-versioned Temporal Tables, new in SQL Server 2016, make such tables behave like any other. How do you create one, or modify an existing table? How can you get an In-Memory Optimized OLTP table to be Temporal? Alex Grinberg shows how. … Read more
Access-control within the database is important for the security of data, but it should be simple to implement. It is easy to become overwhelmed by the jargon of principals, securables, owners, schemas, roles, users and permissions, but beneath the apparent complexity, there is a schema-based system that, in combination with database roles and ownership-chaining, provides a relatively simple working solution.… Read more
Here are seven practical tips for any 'accidental DBA' or developer, faced with having to deploy an upgrade to a database live to production, in a development environment that is in the early stages of getting the database code "house in order", and without any existing 'continuous delivery' process.… Read more
Joe finds a reference to Conway's Game of Life whilst clearing out his desk, and is suddenly gripped with nostalgia. It wasn't just flares, mullets and disco, but simple computer games in interpreted basic. Somehow, Conway s Game of Life was too intriguing to be abandoned in the attic. Can it be implemented in SQL? Joe sets up a challenge.… Read more
SQL Server User-Defined Functions are good to use in most circumstances, but there just a few questions that rarely get asked on the forums. It is a shame, because the answers to them tend to clear up some ingrained misconceptions about functions that can lead to problems, particularly with locking and performanc… Read more
The 'Structured' part of SQL denotes the fact that queries can be nested inside each other in such a way that, wherever you can use a table, you can use a table expression. Such derived tables can provide powerful magic, to which is added CTEs and Lateral Tables. Joe Celko explains.… Read more
Test-Driven Development is a practice that can bring many benefits, including better design, and less-buggy code, but is it relevant to database development, where the process of development tends to me much more interactive, and the culture more test-oriented? Greg reviews the support for TDD for Databases, and suggests that it is worth giving it a try for the range of advantages it can bring to team-working.… Read more
We’ll be looking at a typical database ‘migration’ script which uses an unusual technique to migrate existing ‘de-normalised’ data into a more correct form. So, the book-distribution business that uses the PUBS database has gradually grown organically, and has slipped into ‘de-normalisation’ habits. What’s this? A new column with a list of tags or ‘types’ … Read more
Occasionally, when you install identical databases on two different SQL Server instances, they will behave in surprisingly different ways. Why? Most likely, it is down to different configuration settings. There are around seventy of these settings and the DBA needs to be aware of the effect that many of them have. Brad McGehee explains them all in enough detail to help with most common configuration problems, and suggests some best practices.… Read more
To understand how to write SQL code for SQL Server that performs well, it is important to appreciate how the query optimizer works. Ben Nevarez explains the essentials, in a broad sweep through a complex subject, in an article taken from his new book 'Inside the SQL Server Query Optimizer'.… Read more
Fabiano was asked a couple of questions about SQL Server Distribution Statistics. Having given an answer based on his current knowledge, he then decided to find out for himself whether what he'd said was right, and started an epic journey of exploration into Distribution Statistics and the way that the Query Optimiser uses them.… Read more
Table Value Constructors (TVCs) are a useful feature of 2008, allowing you to specify tables of values and expressions. This has all sorts of uses. Users who are stuck with previous versions of SQL Server can play along, since Rob demonstrates that there have, for a long time, been ways of doing this in SQL Server, though less elegantly.… Read more
There is a popular design for a database that requires a built-in audit-trail of amendments and additions, where data is never deleted, but merely superseded by a later version. Whilst this is conceptually simple, it has always made for complicated SQL for reporting the latest version of data. Alex joins the debate on the best way of doing this with an example using an indexed view and the filtered index.… Read more
Simple-Talk's free wallchart of the most important SSMS keyboard shortcuts aims to help find all those curiously forgettable key combinations within SQL Server Management Studio that unlock the hidden magic that is available for editing and executing queries.
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Subqueries and derived tables can add great versatility to SQL statements, cut down complexity, but can occasionally be a curse when their effect on performance is poorly understood. Surely everyone understands the various types of subqueries and how they are used? If you felt a twinge of doubt, here is Rob Sheldon's easy guide to the subject.
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Simple-Talk generally doesn't re-publish anything from another site, but Troy's popular blog post on the Ten Commandments of Source Control was too good to miss. Here is Troy's updated version in the light of the readers' comments made when it was first published.… Read more
So often, one sees developers doing repetitive coding in SQL Server Management Studio or Visual Studio that would be much quicker and easier by using the built-in Regular-Expression-based Find/Replace functionality. It is understandable, since the syntax is odd and some features are missing, but it is still well-worth knowing about.
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