How many organizations are there?
select count ( organization_id ) from organizations
How many of those organizations are parent organizations?
select organization_id from organizations where organization_id in ( select parent_organization_id from organizations )
Could you tell me how many organizations are not parent organizations of others?
select count ( organization_id ) from organizations where organization_id not in ( select parent_organization_id from organizations )
What is the full name of that organization?
select organization_id from organizations except select parent_organization_id from organizations
What about its organization ID?
select organization_id from organizations except select parent_organization_id from organizations