Function exp 

pub fn exp<'a, V, E>(expr: E) -> SQLExpr<'a, V, Double, E::Nullable, Scalar>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: Numeric,

EXP - returns e raised to the power of the argument.

Returns Double type, preserves nullability.

Example

use drizzle_core::expr::exp;

// SELECT EXP(users.rate)
let exponential = exp(users.rate);