Agile methodologies work well with database developments only if great care is taken to do things right. It requires good judgement and leaves little room for error. Dev Nambi, in an extract from the book Tribal SQL, argues that Agile works for smart, curious, and experienced software engineers.… Read more
It is ironic that one of the most essential of statistical aggregations, the median, has been so difficult in the past to calculate efficiently in SQL. Although the recent window functions provide the solution, there isn't an obviously superior algorithm performance-wise, particularly when working across partitioned sets. Dwain Camps sets the candidates to work and identifies the winners and losers.… Read more
SQL's windowing functions are surprisingly versatile, and allow us to cut out all those self-joins and explicit cursors. Joe Celko explains how they are used, and shows a few tricks such as calculating deltas in a time series, and filling in gaps.… Read more
Before the SQL Window functions were implemented, it was tricky to calculate rolling totals or moving averages efficiently in SQL Server. There are now a number of techniques, but which has the best performance? Dwain Camps gets out the metaphorical stopwatch.… Read more
A Dominoes game of Texas 42 inspires Joe to explore unusual uses for check constraints and views. Sometimes, the best way of discovering useful SQL techniques is to tackle the more unusual problems.… Read more
The words in the documentation for the ALTER TABLE syntax on MSDN are accurate with forensic precision, but the potentially-useful 'syntax diagrams' look, to the untrained eye, to be the result of someone accidentally sitting on the keyboard. The answer for ordinary mortals like us who need to understand the syntax is to have railroad diagrams as well.… Read more
Tables that log a record of what happens in an application can get very large, easpecially if they're growing by half a billion rows a day. You'll very soon need to devise a scheduled routine to remove old records, but the DELETE statement just isn't a realistic option with that volume of data. Hugo Kornelis explains a pain-free technique for SQL Server.… Read more
Many of us have seen, on MSDN, the heading 'Syntax', followed by a rash of nested brackets and keywords, enough to put off the most resolute of code-cutters. However, there is a goldmine of information there, and Phil had an ambition to get at it, and share the gold. The result is this article, full of railroad diagrams… Read more
Parts explosions present a classic IT problem. How can one calculate such things as weight or cost of assemblies in SQL? Joe shows how it can be done using nested sets, with not an IDENTITY or GUID in sight..… Read more
There are several frameworks for assisting with the testing of SQL Server databases, but tSQLt is popular because it is written in TSQL and is simple for a database developer to set up and use. It doesn't get in the way. Rob Sheldon shows you how to get started. … Read more
Pivoting SQL Server tables is always awkward, even with the PIVOT and UNPIVOT operators. If you want to get the job done without GROUP BY or PIVOY, here is a way to do it using only REPLACE.… Read more
What should you do if your first, most intuitive solution to a problem ends up scanning the data more than is necessary, resulting in poor performance? Have you missed a new SQL Server feature that can remove inefficiency from your technique? Alternatively, do you need a little help, and some lateral thinking, to open the path to a different approach? Sometimes, the answer is "both".… Read more
For some time, Microsoft had a few window functions, but not the full set specified in the SQL 2003 standard. Now, in SQL Server 2012 we have the whole range, and extremely useful they are too. There's no longer an excuse to avoid them, particularly now you have Rob's gentle introduction.… Read more
It should be easy to model a game of poker in SQL. The problem is, however, that you need to model a permutation from a set of elements. Joe Celko argues that using a group of columns to do this isn't necessarily a violation of 1NF, since a permutation is atomic. Then comes the second problem: how would you sort such a column-base permutation in order? Sorting columns in SQL?… Read more
Relational Databases have tables as data structures, not arrays. This makes it tricky and slow to do matrix operations, but it doesn't mean it is impossible to do. Joe gives the Celko Slant on how to go about doing Matrix Math in SQL.… Read more
Sparse columns and column sets in SQL Server 2012 provide a way of accomodating the less-structured data that has always proved to be tricky for the relational model. They can be used very effectively where the attributes are sparse for any given entity and very numerous across all entities. Seth Delconte shows how to use them.… Read more
The database developer can, of course, throw all errors back to the application developer to deal with, but this is neither kind nor necessary. How errors are dealt with is very dependent on the application, but the process itself isn't entirely obvious. Phil became gripped with a mission to explain...… Read more
Following up from his popular article, SQL View Basics, Joe delves into the main uses of views, explains how the WITH CHECK OPTION works, and demonstrates how the INSTEAD OF trigger can be used in those cases where views cannot be updatable.… Read more
