TSQL Howto get count of unique users ?

Question

This is really dumb question but still my head cannot work it out. I have a table with Orders, each order has userID in it. User can have unlimited amount of Orders. How do i make count of unique userIDs ?

Answer 1

You can;

SELECT COUNT(DISTINCT userID) 
FROM Tbl

You can give the count column a name by aliasing it:

SELECT COUNT(DISTINCT userID)  NumberOfDistinctUsers
FROM Tbl

Answer 2

select count(*) from
(select distinct userid form ordertable) d

Answer 3

can you show the schema for your tables?