To clean out unwanted contact data from your collection databases, there are some referential integrity constraints that mean the deletions have to happen in a specific order. The following query will delete all contacts, facets, interactions, interaction facets, and contact identifiers from xDB.

  delete
  FROM [xdb_collection].[ContactIdentifiers]
  
  delete
  FROM [xdb_collection].[ContactIdentifiersIndex]

  delete
  FROM [xdb_collection].[ContactFacets]
    
  delete
  FROM [xdb_collection].[InteractionFacets]
  
  delete
  FROM [xdb_collection].[Interactions]

  delete
  FROM [xdb_collection].[Contacts]

You will need to run this on both Collection shards.