MySQL: Is there a performance hit comparing numbers with an important precision -


i'm wondering in mysql if better performance compare numbers important precision or round them before comparing, knowing comparison precision less important compared numbers precision.

ex: 

select 0.123456789101112123456789101112 < 0.987654321012345987654321012345

or

select round(0.123456789101112123456789101112,2) < round(0.987654321012345987654321012345,2)

there's performance hit in version uses round().

first, calling function more expensive not calling function.

second, , possibly more significantly, if there's index on column, can't used if perform function on column before comparing something.

but getting right answer practically more important using efficient method.


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