SQL Server Performance Tuning

Wasting CPU For Implicit Conversions In SQL Server

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Written by
Mark Varnas

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What is the SQL Server implicit conversion?

It occurs when the SQL Server needs to convert the value of variables or columns to another data type for comparison.

Usually, when you mismatch data types in a WHERE clause or JOIN condition of the query.

Why should you care about them?

Your indexes will not be used efficiently.

You will waste CPU resources in the conversion process unnecessarily.

Which means that queries run slower.

How can I find them?

Figure out the slow queries of your server and review the execution plans found.

As you can see below, you can easily find the implicit conversions (implicit conversions Warnings) in the query plan.

Figure 1 - Implicit conversion warning in the query plan
Figure 1 – Implicit conversion warnings in the query plan

How to fix them?

More information:

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Article by
Mark Varnas
Founder | CEO | SQL Veteran
Hey, I'm Mark, one of the guys behind Red9. I make a living performance tuning SQL Servers and making them more stable.

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