SELECT COUNT(*)
FROM dbo.Badges AS b
JOIN dbo.Comments AS c
ON b.UserId = c.UserId
OPTION(MERGE JOIN, RECOMPILE);
WITH Comments AS
(
SELECT DISTINCT c.UserId
FROM dbo.Comments AS c
)
SELECT COUNT(*)
FROM dbo.Badges AS b
JOIN Comments AS c
ON b.UserId = c.UserId
OPTION(MERGE JOIN, RECOMPILE)