How do I count the number of rows that have different dates

Question

I want to count the total numbers of row in SQL database.

"tableA" :

   id | date       | 
   ---+------------+
    1 | 2019-09-03 | 
    2 | 2019-09-03 | 
    3 | 2019-09-04 | 
    4 | 2019-09-05 | 

I want to execute it as new column name "total" that should have like this :

 total
 -----
   3

because they are 3 different dates.

I know that the result must use 2 query like this:

SELECT date 
FROM tableA 
GROUP BY date AS total;

SELECT COUNT(total) 
FROM tableA;

How to combine 2 queries like that or there is another way?

Answer 1

使用count(distinct date)

SELECT COUNT(distinct date) FROM tableA

Answer 2

select count( distinct date) as total from tableA;