Ignoring Tickets without SLA Assessments
In the published guidelines for building an example SLA Performance Dashboard you'll notice our metrics and reports are careful not to include any tickets if an SLA assessment has yet to be made since we aren't interested in anything that doesn't have an SLA assessment: Metrics, i.e. we are only concerned with tickets that have either passed or violated the SLA event.
In this way we can ensure that performance measurements don't include any tickets where an SLA assessment has yet to be made including tickets that will never be assessed because they were closed and merged before an assessment was made.
We therefore recommend this approach is adopted when crating your own SLA performance metrics and reports.
Igonring All Closed & Merged Tickets
Of course there might be cases in which a ticket is merged and closed into another ticket after an SLA Assessment has been made on one or more events, in which case the SLA Measure will be marked as passed or violated.
Depending upon your own policy and reporting requirements you might chose to ignore the SLA assessments for all closed and merged tickets when calculating your performance measurements so that only the main/original ticket is measured.
You will notice that when a ticket is closed and merged Zendesk tags the ticket with 'closed_by_merge' so if this is your preference we recommend updating your SLA metrics as follows: