SQL query that gives me the count of records with unique column value in table

Question

I am new to SQL and learning some basic things with Treasure Data. I have many records of reservation in a table with 11 distinct resource values that users can reserve.

This gives me the resources in a table:

SELECT 
  DISTINCT resource
FROM
  reservation
;

But what if I just want the output to be the number of records that get returned by the query (i.e., "11").

This doesn't work:

SELECT 
  COUNT(*) DISTINCT resource
FROM
  reservation
;

What is the right syntax for this? I have not been able to figure this out.

Answer 1

The distinct keyword goes inside the aggregate function:

SELECT 
  COUNT(DISTINCT resource)
FROM
  reservation
;