SQL计算一列中唯一值的数量并对该信息求和

Question

I am trying to make a sum of the count of different values.

Here's an example :

 a a a b b b c c c d d d d e e e e 

The output would be :

5

Because there's 5 different values in that column.

Answer 1

Perform a Distinct Count which should give you the count of distinct values in a column and no need to do sum here

select count(distinct colname) 
from yourtable

Answer 2

After searching and giving some good tought and testing here's the correct query :

SELECT SUM(uniqueValues) FROM (SELECT COUNT(DISTINCT values) as uniqueValues FROM tablename GROUP BY values)