Phil Factor in Theory and design Concepts and Issues in Test Data Generation Data generation is the science and art of providing data for database development work that is as realistic and controllable... 10 June 2024 11 min read
Theory and design Joe Celko in Theory and design The CHECK() Constraint One of the many ways a relational table differs from the file structures used by pre-relational storage systems is that... 20 May 2024 11 min read
Theory and design Phil Factor in Theory and design Database Subsetting and Data Extraction Let’s start by defining a subset and why you would require a data subset? When dealing with the development, testing... 17 April 2024 11 min read
Theory and design Joe Celko in Theory and design SQL Logic In this article, I will discuss the history and thinking behind several types of logic that are typically associated with... 29 March 2024 13 min read
Theory and design Joe Celko in Theory and design Department of Redundancy Department Ever wonder all the reasons that we use databases instead of file systems? While we don’t think of it too... 18 March 2024 12 min read
T-SQL Programming Itzik Ben-Gan in T-SQL Programming Two-Dimensional Interval Packing Challenge Packing intervals is a classic SQL task that involves packing groups of intersecting intervals to their respective continuous intervals. In... 02 January 2024 17 min read
PostgreSQL Boris Novikov in PostgreSQL Eager Aggregation in SQL queries Aggregation is a widely used way to summarize the content of a database. It is usually expressed with GROUP BY... 27 December 2023 15 min read
Theory and design Phil Factor in Theory and design Using a SQL Tokenizer Imagine this: you have several directories full of SQL script files, and you need to know where a certain table... 18 December 2023 9 min read
T-SQL Programming Aaron Bertrand in T-SQL Programming When an update doesn’t update Tell me if you’ve heard this one before: I changed data from my application, but when I checked the database,... 27 November 2023 5 min read
Theory and design Joe Celko in Theory and design The NTILE Function The SQL NTILE() is a window function that allows you to break a table into a specified number of approximately... 09 November 2023 8 min read
Theory and design Joe Celko in Theory and design First Normal Form Gets No Respect Dr. Codd first described the relational model in a paper in Communications of the ACM (CACM 13 No 6; June... 05 October 2023 13 min read
T-SQL Programming Itzik Ben-Gan in T-SQL Programming T-SQL Fundamentals: Controlling Duplicates When people start learning a new field, for example T-SQL, it’s tempting to spend very little time trying to understand... 28 September 2023 20 min read
Theory and design Joe Celko in Theory and design The GROUP BY Clause When you’re learning SQL DML, the most complicated clause is typically the GROUP BY. It’s a fairly simple grouping based... 10 July 2023 27 min read
Theory and design Joe Celko in Theory and design Getting Out of Character In this article, Joe Celko gives us a history of the different character sets that are used in computing and... 28 February 2023 13 min read
Theory and design Joe Celko in Theory and design The VALUES clause or building tables out of nothing The VALUES clause makes inserting literal values into a table simple and easy. In this article, Joe Celko explains how... 23 May 2022 6 min read
Theory and design Joe Celko in Theory and design Combinations, permutations, and derangements Joe Celko explains how several mathematical concepts, combinations, permutations, and derangements, relate to databases.… 03 May 2022 8 min read
Theory and design Joe Celko in Theory and design The problem with averages Everyone learns to calculate an average in school, but, as Joe Celko shows, there are better ways to summarize data.… 01 March 2022 8 min read
Learn SQL Server Greg Larsen in Learn SQL Server How to replace an identity column with a sequence number SQL Server provides two ways to include an incrementing number in a table. Greg Larsen explains how to replace an... 04 January 2022 16 min read
Theory and design Joe Celko in Theory and design Much Ado about nothing: missing data Joe Celko explains how missing data is handled from the printing press to databases.… 01 July 2021 13 min read
Theory and design Joe Celko in Theory and design Constraints and declarative referential integrity Database systems have powerful features built right in that can ensure the integrity of data. In this article, Joe Celko... 06 May 2021 14 min read