Articles

External Article

Eager Aggregation in SQL queries

Aggregation is a widely used way to summarize the content of a database. It is usually expressed with GROUP BY clause or just using aggregate functions (like COUNT or SUM). When the database engine executes a query with aggregations, it produces individual rows need to compute the required output and then performs the aggregation as (almost) last step. We discuss in this article how to re-write a query manually so that the order of operations will be different and when it can be beneficial.

2024-01-15

Technical Article

Always On Availability Groups Troubleshooting and Monitoring Guide

This guide helps you get started on troubleshooting some of the common issues in AlwaysOn Availability Groups and monitoring AlwaysOn Availability Groups. It is intended to provide original content as well as a landing page of useful information that is already published elsewhere.

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2024-01-09 (first published: )

Technical Article

Customizing Statistics Histogram in SQL Server 2019

The use of statistics in SQL Server is tightly embedded in the query optimizer and query processor. The creation and maintenance of statistics is usually handled by the SQL Server engine, though many DBAs and developers know that periodically we might need to update those statistics to ensure good performance of queries. SQL Server 2019 gives us more options.

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2024-01-09 (first published: )

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Question of the Day

The LAGging NULL

I have this data in a SQL Server 2022 table: 

player         yearid team HR
Alex Rodriguez 2012   NYY  18
Alex Rodriguez 2013   NYY  7
Alex Rodriguez 2014   NYY  NULL
Alex Rodriguez 2015   NYY  12
Alex Rodriguez 2016   NYY  9
If I run this code, what are the results returned in the hrgrowth column? 
SELECT
  player
, yearid
, hr
, hr - LAG (hr, 1, 0) IGNORE NULLS OVER (ORDER BY yearid) AS hrgrowth
FROM dbo.playerstats;

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