Do you mean like this?

SELECT    SUM(value)
FROM      myTable

If you have multiple columns to return, simply add each non-aggregate (i.e., summed) row to the GROUP BY clause:

SELECT    firstName, lastName, SUM(value)
FROM      myTable
GROUP BY  firstName, lastName

To answer this, I did the following.

mysql> CREATE TABLE myid(id INT, myname VARCHAR(10));
Query OK, 0 rows affected (0.35 sec)

mysql> INSERT INTO myid VALUES (1, 'Paul');
Query OK, 1 row affected (0.06 sec)
mysql> INSERT INTO myid VALUES (2, 'Peter');
Query OK, 1 row affected (0.07 sec)

mysql> CREATE TABLE myrating(ratename VARCHAR(10), therating INT);
Query OK, 0 rows affected (0.43 sec)

mysql> INSERT INTO myrating VALUES('Paul', 3);
Query OK, 1 row affected (0.05 sec)
mysql> INSERT INTO myrating VALUES('Paul', 4);
Query OK, 1 row affected (0.04 sec)
mysql> INSERT INTO myrating VALUES('Peter', 6);
Query OK, 1 row affected (0.06 sec)
mysql> INSERT INTO myrating VALUES('Peter', 456);
Query OK, 1 row affected (0.06 sec)

And then performed the query

SELECT myid.myname, SUM(myrating.therating) AS The_Rating 
FROM myid inner 
JOIN myrating 
ON myrating.ratename = myid.myname 
GROUP BY myid.myname;

Obtaining the result:

+--------+------------+
| myname | The_Rating |
+--------+------------+
| Paul   |          7 |
| Peter  |        462 |
+--------+------------+
2 rows in set (0.04 sec)

Does this satisfy your requirements?

SELECT SUM(grand_total) FROM order

Here is a reference to aggregate functions in MYSQL.

You can use WITH ROLLUP modifier:

select coalesce(user_type, 'total') as user, count(*) as count
from users
where user_type in ('driver', 'passenger')
group by user_type with rollup

This will return the same information but in a different format:

user      | count
----------|------
driver    |    32
passenger |    58
total     |    90

db-fiddle

In MySQL 8 you can use COUNT() as window function:

select distinct
  user_type,
  count(*) over (partition by user_type) as count,
  count(*) over () as sum
from users
where user_type in ('driver', 'passenger');

Result:

user_type | count | sum
----------|-------|----
driver    |    32 |  90
passenger |    58 |  90

db-fiddle

or use CTE (Common Table Expressions):

with cte as (
  select user_type, count(*) as count
  from users
  where user_type in ('driver', 'passenger')
  group by user_type
)
select user_type, count, (select sum(count) from cte) as sum
from cte

db-fiddle

You can create a special record with your sum and add it at the end of your first query

SELECT * FROM `table` WHERE `date` > '14-01-01' AND `date` < CURDATE()
UNION
SELECT 9999, CURDATE(), SUM(`amount`) FROM `table` WHERE `date` < CURDATE()

Then you will have all your desired record and the record with id 9999 or whatever is your sum