Using IsUnique on _Open and _Click

What IsUnique means

IsUnique = 1 indicates the first open or first click a subscriber recorded for that send job (at the engagement grain). Total opens/clicks include repeats — critical distinction for rate denominators.

Unique open rate example

SELECT
  s.JobID,
  COUNT(DISTINCT s.SubscriberKey) AS Sent,
  SUM(CASE WHEN o.IsUnique = 1 THEN 1 ELSE 0 END) AS UniqueOpens
FROM _Sent s
LEFT JOIN _Open o
  ON s.JobID = o.JobID
  AND s.ListID = o.ListID
  AND s.BatchID = o.BatchID
  AND s.SubscriberID = o.SubscriberID
WHERE s.EventDate >= DATEADD(day, -30, GETDATE())
GROUP BY s.JobID

Reporting guidance

• Use IsUnique for standard campaign open/click rates.
• Omit IsUnique when analyzing repeat engagement or time-between-opens.
• The SQL Sandbox can inject unique-event predicates when selected tables support them.