What source system code includes the sub string 'en'?
select distinct source_system_code from cmi_cross_references where source_system_code like '%en%'
What are the other sub strings, that do not contain 'en'?
select distinct source_system_code from cmi_cross_references where source_system_code not like '%en%'
What is the master id please.
select master_customer_id from cmi_cross_references where source_system_code = 'Electoral'