public static <T extends Number> WindowOver<T> stddevSamp(Expression<T> expr) {
        return new WindowOver<T>(expr.getType(), SQLOps.STDDEVSAMP, expr);
    }
returns the cumulative sample standard deviation and returns the square root of the sample variance.

@param expr argument
@return stddev_samp(expr)
querydsl-sql/src/main/java/com/querydsl/sql/SQLExpressions.java