Why casting from float to varchar is being rounded in SQL Server

Question

Following sql

declare @a as float, @b as float

select @a=1.353954 , @b=1.353956
select 
CAST(@a as VARCHAR(40)) AS a_float_to_varchar ,
CAST(@b as VARCHAR(4         


        

Answer 1

cast to decimal before casting to varchar:

declare @a as float, @b as float

select @a=1.353954 , @b=1.353956
select 
CAST(CAST(@a AS DECIMAL(38,18)) as VARCHAR(40)) AS a_float_to_varchar ,
CAST(CAST(@b AS DECIMAL(38,18)) as VARCHAR(40)) AS b_float_to_varchar