SQL Window Functions Series: LAG() and LEAD()
Dive deep into the powerful SQL window functions, LAG() and LEAD(). Explore their intricacies, discover real-world examples, and avoid common pitfalls.
2023-12-11
9,019 reads
Performance
PerfMon: Using SQL Server Performance Counters
Learn how you can use Windows Performance Monitor and the PAL to gather metrics from your SQL Server instances.
2022-07-20
23,627 reads
Automating Extended Events data collection
It’s not difficult to set up an extended event session, but reviewing and saving the data can be complex. In this article, Edward Pollack demonstrates how to collect extended event data.
2021-11-03
SQL Compilations/sec is not what you think it is
SQL Server perfmon counters provide a wealth of information about performance. In this article, Fabiano Amorim shows how current wisdom about one counter, SQL Compilations/sec, can sometimes be misleading.
2021-08-20
SQL Server performance monitor data: Introduction and usage
Monitoring SQL Server for performance is a critical part of a DBA’s job. In this article, Edward Pollack explains some of the SQL Server performance monitor data and how to collect it.
2021-07-21
SQL Server plan cache mining – Plan attributes
Edward Pollack demonstrates how SQL Server plan cache mining can uncover a wealth of information to help with troubleshooting performance issues.
2021-05-21
Efficiently Polling Remote Data Sources
In this article, Edward Pollack describes some of the issues when querying against remote data sources. He covers remote SQL Servers and also connecting to a PostgreSQL database.
2020-10-30
Optimizing Your Query Plans with the SQL Server 2014 Cardinality Estimator
SQL Server 2014 introduces the first major redesign of the SQL Server Query Optimizer cardinality estimation process since version 7.0. The goal for the redesign was to improve accuracy, consistency and supportability of key areas within the cardinality estimation process, ultimately affecting average query execution plan quality and associated workload performance. This paper provides an overview of the primary changes made to the cardinality estimator functionality by the Microsoft query processor team, covering how to enable and disable the new cardinality estimator behavior, and showing how to troubleshoot plan-quality regressions if and when they occur.
2018-06-26
2,974 reads
READ COMMITTED SNAPSHOT ISOLATION and High version_ghost_record_count
Developer shops may decide to use Read Committed Snapshot Isolation (RCSI) to reduce contention, and possibly improve performance, but it is not without its own pitfalls. In this article, Uwe Ricken describes a situation where long running transactions caused a severe performance degradation when RCSI was in use.
2018-03-26
3,103 reads
2018-06-05 (first published: 2018-01-11)
2,181 reads
Blogs
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Forums
UNISTR Escape
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Celebrating Tomorrow
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SQL Art: I Made a Christmas Card In SSMS
Comments posted to this topic are about the item SQL Art: I Made a...
Question of the Day
UNISTR Escape
In SQL Server 2025, I run this command:
SELECT UNISTR('*3041*308A*304C\3068 and good night', '*') as "A Classic";
What is returned? (assume the database has an appropriate collation)
A: 
B: 
C: 
See possible answers