Warning in query plan “Cardinality Estimate”
Question
create table T(ID int identity primary key)
insert into T default values
insert into T default values
go
select cast(ID as varchar(10)) as ID
from T
where ID = 1
The query above has a warning in the query plan.
<Warnings>
<PlanAffectingConvert ConvertIssue="Cardinality Estimate" Expression="CONVERT(varchar(10),[xx].[dbo].[T].[ID],0)" />
</Warnings>
Why does it have the warning?
How could a cast in the field list affect the cardinality estimate?
No correct solution
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