TSQL Count 'Where' Condition

Question

How do I implement the 'meaning' of the following psuedo-SQL statement:

COUNT(distinct id where attribute1 > 0)

In other words, how do I make conditional, distinct counting statements?

Thanks!

Answer 1

Well, if you can filter the entire query, then LittleBobbyTables already has the answer for you. If not, you can get that column like so:

count(distinct case when attribute1 > 0 then id end) -- implicit else null

Answer 2

You pretty much had it:

SELECT COUNT(DISTINCT [ID]) AS DistinctID
FROM YourTable
WHERE attribute1 > 0