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)
5,190 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
3,118 reads
A good example where the Query optimizer picks the wrong query plan and suggested index.
2021-02-25
4,543 reads
Continued analysis of index architecture with revised clustered index. Part 2 of Column Order Indexes
2020-12-11 (first published: 2019-04-24)
2,520 reads
Ever wonder about index column order; this piece should give some insight.
2020-12-04 (first published: 2019-02-28)
8,007 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)
7,700 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
4,298 reads
2020-03-03 (first published: 2019-11-25)
9,980 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
3,721 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
8,227 reads
By Steve Jones
I love Chicago. I went to visit three times in 2023: a Redgate event,...
By Brian Kelley
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Hello I need to get txt files from directory and send email, when I...
Hello, I have a question regarding Availability group server architecture. A little background: We...
Let’s consider the following script that can be executed without any error on both SQL Sever and PostgreSQL. We define the table t1 in which we insert three records:
create table t1 (id int primary key, city varchar(50)); insert into t1 values (1, 'Rome'), (2, 'New York'), (3, NULL);If we execute the following query, how will the records be sorted in both environments?
select city from t1 order by city;See possible answers