Picking the ON or WHERE Clause for the SQL Predicate

Helping people solve T-SQL problems is one of my favorite hobbies. Someone messaged me the other day with a complex query that was almost complete except for one issue. He needed to perform a LEFT OUTER JOIN but had to filter based on a value from the right table. However, when he added the filter, SQL removed rows from the left table. The task was to decide where to place the SQL predicate: in the ON or WHERE clause.

From Rows to Pages: The Hidden Chaos Behind SQL Server’s Sampling Methods

Learn about the TABLESAMPLE option in T-SQL and uncover some of the pitfalls of assuming this works as you think it does.

A Big Updated Columns List

Split strings by Regular Expressions in SQL Server 2025

SQL Server users have been asking for native regular expression support for over two decades. There are third-party Common Language Runtime (CLR) modules that offer this functionality, but these can be complicated to install and simply aren’t possible in some environments. I want to split a string using a regular expression instead of a static string. Will that be possible in SQL Server 2025, without CLR?

Getting the SQL

Getting Azure SQL Database Permissions

The Updated Columns List

DISTINCT and UNION: What happens when you use them together?

When I was perusing my LinkedIn feed the other day, I came across this thread about using SELECT *. In one of the replies, Aaron Cutshall noted that: “Another real performance killer is SELECT DISTINCT especially when combined with UNION. I have a whole list of commonly used hidden performance killers!”

Multiple Defaults

Adding Defaults