Performance and Tuning

External Article

Index Scans and Table Scans

  • Article

There are several things that you can do to improve performance by throwing more hardware at the problem, but usually the place you get the most benefit from is when you tune your queries. One common problem that exists is the lack of indexes or incorrect indexes and therefore SQL Server has to process more data to find the records that meet the queries criteria. These issues are known as Index Scans and Table Scans.

2025-06-06

Technical Article

Improve Query Performance when SQL Server Ignores Nonclustered Index

  • Article

Do you wonder why SQL Server ignores an index? Do you think about how you can deal with this problem? When you include too many columns in a query you decrease index selectivity. So, if you write a query like “Select * From …” the chance of choosing your nonclustered index will decrease.

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2025-03-03

SQLServerCentral Article

The Paradox of NOLOCK: How Dirty Reads Can Sometimes Be Cleaner

  • Article

Every SQL Server developer has heard it: "Don't use NOLOCK in production!" But this common rule isn't as simple as it seems. Sometimes, what seems like a bad practice can actually be the right choice. Let's explain what NOLOCK really does in simple terms. When you use NOLOCK, you're telling SQL Server "just show me […]

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2024-12-09

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Question of the Day

Adding Defaults

I have a table, called dbo.logger, in SQL Server 2022. I decide to add two new columns to this table with this code.

ALTER TABLE dbo.logger ADD CreateDate DATETIME CONSTRAINT dfGetDate DEFAULT GETDATE()
GO
ALTER TABLE dbo.logger ADD ModifyDate DATETIME DEFAULT dfGetDate
GO
What happens when I run these two batches?

See possible answers