While preparing for my SQL Saturday Salt Lake City presentation, Climbing the B-Tree, I ran into one of the “word of mouth” facts that the first column of an index should be highly selective, i.e., it should only point to one or a few rows. This is not always the case and I’ll show you […]
2023-01-02 (first published: 2020-09-16)
5,545 reads
In the last year I’ve published articles on indexes to include Indexes: When Column Selectivity Is Not Always A Requirement – SQLServerCentral and Query Optimizer Suggests Wrong Index and Query Plan -- Why? – SQLServerCentral. This article is a continuation of just how the optimizer interacts with the index wizard. We’ve all heard and read […]
2021-07-07
3,678 reads
A good example where the Query optimizer picks the wrong query plan and suggested index.
2021-02-25
5,050 reads
Continued analysis of index architecture with revised clustered index. Part 2 of Column Order Indexes
2020-12-11 (first published: 2019-04-24)
2,574 reads
Ever wonder about index column order; this piece should give some insight.
2020-12-04 (first published: 2019-02-28)
8,683 reads
Is there a difference between using TOP and MAX/MIN to return and end value to a table?
2020-08-14 (first published: 2018-12-17)
7,873 reads
In Part 1 of this article we looked at a specific use case (probably exaggerated) that gave us an idea about how CPU and IO performance might be affected by a bad page split. We continue this analysis looking at what really happens to the data on the leaf pages of a clustered index with […]
2020-07-02
4,478 reads
2020-03-03 (first published: 2019-11-25)
10,687 reads
Introduction Fill Factor is a parameter most of us have ignored because there is no definitive way to calculate what the correct value should be. Part 1 of this series describes a new technique to dynamically determine index fill factors for all indexes within a database. Part 2 covers an analysis of the data collection […]
2019-08-27
3,944 reads
Introduction So what’s all the fuss about Fill Factor? It is a SQL Server parameter I’ve ignored for 20+ years. The main reason was/is I’ve had no idea about what value to use. There is just no documented definitive guidance. Back in April at SQL Saturday #830 - Colorado Springs, I attended two sessions by […]
2019-08-20
8,868 reads
By Steve Jones
Superheroes and saints never make art. Only imperfect beings can make art because art...
One feature that I have been waiting for years! The new announcement around optimize...
Following on from my last post about Getting Started With KubeVirt & SQL Server,...
Hi, in a simple oledb source->derived column->oledb destination data flow, 2 of my...
hi, i noticed the sqlhealth extended event is on by default , and it...
Using New-AzSqlInstanceServerTrustCertificate to import a certificate and get the message New-AzSqlInstanceServerTrustCertificate: Long running operation...
I am currently working with Sql Server 2022 and AdventureWorks database. First of all, let's set the "Read Committed Snapshot" to ON:
use master; go alter database AdventureWorks set read_committed_snapshot on with no_wait; goThen, from Session 1, I execute the following code:
--Session 1 use AdventureWorks; go create table ##t1 (id int, f1 varchar(10)); go insert into ##t1 values (1, 'A');From another session, called Session 2, I open a transaction and execute the following update:
--Session 2 use AdventureWorks; go begin tran; update ##t1 set f1 = 'B' where id = 1;Now, going back to Session 1, what happens if I execute this statement?
--Session 1 select f1 from ##t1 where id = 1;See possible answers