SQL  EXP()
Exponential is a mathematical function
which is almost always understood to mean the natural exponential function. The
function EXP() returns the exponential value for the numeric expression. I have
come across the EXP built in function in SQL Server and this function plays a
very important role in data analytics calculations.
This function has one mandatory argument
and it returns float type exponential value. In SQL, we have use the following
syntax:
SQL Syntax: EXP(Argument)
Argument: Any numeric
expression.
Return Type: float.
Note: If value is numeric
and not equal to zero then it will return float type otherwise it will return
1 for the 0 value. if argument is null then return type should be null.

The exponential function is equal to e^{x}. The value for the constant float number e is approximately
2.718281828 (natural logarithm).
 declare local veriables
declare @inpfloat float=1.2,
@inpInt INT=1,
@inpDecimal Decimal=1.2
 output parameters
select EXP(@inpfloat) as 'Float EXP()',
EXP(@inpINT) as
'Int EXP()',
EXP(@inpDecimal) as 'Decimal EXP()'
 set value 0 for veriable
SET @inpfloat=0
SET @inpInt=0
SET @inpDecimal=0
 output parameters
select EXP(@inpfloat) as 'Float EXP()',
EXP(@inpINT) as
'Int EXP()',
EXP(@inpDecimal) as 'Decimal EXP()'
We can view the
difference on the above results. this is because 0 is to
the power anything is equal to 1.

Conclusion
In simple words EXP() function is used to
get the value of e ^ x because Exp expects a float and returns one, so the
results from a decimal type include an implicit conversion to and from float
and in turn this behaviour is due to inherent imprecision of FP numbers.