The uniquifier is a hidden 4-byte value that SQL Server adds to duplicate keys in a non-unique clustered index. This post measures its real cost row by row on SQL Server 2025 and shows it on the page. It also compares it with a unique key you choose yourself.
BETWEEN vs IN in SQL Server: Which One Reads Less?
BETWEEN vs IN looks like a style choice, and it is not. This post builds a demo table and measures BETWEEN, the two operators and an IN list with and without an index. It shows that BETWEEN and the operators share one plan, that IN seeks once for every value and that sparse values change the question.
SQL SERVER – Delete Statement and Index Usage
An index can help a DELETE statement locate rows to remove. A customer asked whether indexes benefit modifications alongside SELECT queries.
Nonclustered Primary Key – SQL in Sixty Seconds #119
I will describe in detail a bit later on during this blog post. Today we are going to learn that it is possible to have a nonclustered primary key.
What Happens If the Clustered Index is Disabled? – Interview Question of the Week #291
Question: What Happens If the Clustered Index is Disabled?
Answer: If you disable the clustered index, you can’t retrieve data from the table.
Alter Index Add Column – Workaround – SQL in Sixty Seconds #097
However, while modifying it we faced a unique challenge that we can’t actually alter index to add columns. Let us discuss that today.
Statistics That Never Auto Update: Find the NORECOMPUTE Flag
Statistics that never auto update usually carry a hidden NORECOMPUTE flag, set when an index was created. This post builds a demo table, shows the flagged statistic go stale while its neighbor updates itself, and lists every flagged statistic in a database. It also shows which maintenance commands clear the flag and which keep it.