Type conversion in expression may affect cardinality estimate in query plan

Question

I have a warning in my Execution plan that I can not get rid of. I've made an Minimal, Reproducible Example here:

declare @TestData Table
(
  FloatValue float null
)

insert into @TestData values
 (null), (0.1)

select 
    CONVERT(varchar, FloatValue * 100.00) + ' pct.' PctValue
from 
    @TestData

I've included the warning.

Answer 1

SQL Server is sometimes a little over cautious with its warnings.

You can encounter various warnings in the execution plan that, after review, prove to be irrelevant; for example you may sometimes see a warning about an excessive memory grant, even though the grant is literally the minimum configured amount possible per query.

As this is not a column involved with filtering or joining decision making you can safely disregard it.

Answer 2

You can change CONVERT(varchar, FloatValue * 100.00) to FORMAT(FloatValue * 100.00, 'N0') in the query:

declare @TestData Table
(
  FloatValue float null
)

insert into @TestData values
 (null), (0.1)

select 
    FORMAT(FloatValue * 100.00, 'N0') + ' pct.' PctValue
from 
    @TestData

And it will get rid of the warning: