OP09: Observation period records per person

List all people (person_id) who has specific number of observations. The input to the query is a value (or a comma-separated list of values) for a record count.  

Input:
 Parameter  Example  Mandatory  Notes
observation_count 3  Yes  Number of observation periods

Sample query run:
The following is a sample run of the query. The input parameters are highlighted in blue.
SELECT 
  p.person_id,
  count(1) observation_period_count
FROM observation_period p
GROUP BY p.person_id
having count(1) = 3
Output:
Output field list:
 Field  Description
person_id Person identifier
observation_period_count Number of periods

Sample output record:
 Field  Value
person_id  826002
observation_period_count  3
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