Statistics in SQL: The Mann–Whitney U test
Phil Factor shows how to use the Mann-Whitney U test in SQL to to find out whether two samples come from the same distribution.
2017-09-04
4,456 reads
T-SQL
2017-08-31
1,149 reads
2017-08-22
1,202 reads
Statistics in SQL: The Kruskal–Wallis Test
Before you report your conclusions about your data, have you checked whether your 'actionable' figures occurred by chance? The Kruskal-Wallis test is a safe way of determining whether samples come from the same population, because it is simple and doesn't rely on a normal distribution in the population. This allows you a measure of confidence that your results are 'significant'. Phil Factor explains how to do it.
2017-07-27
6,123 reads
The Basics of Good T-SQL Coding Style – Part 2: Defining Database Objects
Technical debt is a real problem in database development, where corners have been cut in the rush to keep to dates. The result may work but the problems are in the details: such things as inconsistent naming of objects, or of defining columns; sloppy use of data types, archaic syntax or obsolete system functions. With databases, technical debt is even harder to pay back. Robert Sheldon explains how and why you can get it right first time instead.
2017-07-25
5,860 reads
SQL Server User-Defined Functions
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.
2017-07-21
5,686 reads
Simple SQL: Attribute Splitting
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.
2017-07-18
3,822 reads
2017-07-17
1,268 reads
2017-07-13
1,030 reads
2017-07-11
1,184 reads
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Creating JSON II
On SQL Server 2025, what happens when I run this code:
SELECT JSON_OBJECTAGG( N'City':N'Denver' RETURNING JSON) GOSee possible answers