First, the numerator and/or denominator are converted to a type with decimal precision greater than 8. Decimal, numeric and floating point can be used.

Then do division calculation and convert the calculation result into 8 decimal places.

Select convert (decimal (18,8), convert (decimal (18,8), 1)/3).

select convert(decimal( 18，8)， 1/convert(decimal( 18，8)，3))

Select conversion (decimal (18,8), conversion (floating point, 1)/3)

select CONVERT(decimal( 18，8)， 1/convert(float，3))