Blitz Result: Implicit Conversion Found in the Plan Cache

If you compare a string with a number, like this:

SELECT * FROM dbo.Customers WHERE MyNumericIDField = '1234'

SQL Server has to think about which side of the equation should be converted.  Should we convert MyNumericIDField to a string, or convert the string ‘1234’ to a number?  Sometimes, based on the way we pass in our queries, SQL Server has its hands tied and converts the wrong side – like converting an entire table to match your input parameters.

This part of our SQL Server sp_Blitz script checks the plan cache looking for resource-intensive queries that are doing implicit conversions.

To Fix the Problem

Read about Identifying and Correcting SQL Server Implicit Conversions, then review the execution plans found by sp_Blitz.  You can often change the query parameters or variable datatypes to make them match the table.

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