CREATE TABLE benefits_overpayments (council_tax_id NUMBER, cmi_cross_ref_id NUMBER)
CREATE TABLE cmi_cross_references (cmi_cross_ref_id NUMBER, master_customer_id NUMBER, source_system_code CLOB)
CREATE TABLE business_rates (business_rates_id NUMBER, cmi_cross_ref_id NUMBER)
CREATE TABLE parking_fines (council_tax_id NUMBER, cmi_cross_ref_id NUMBER)
CREATE TABLE rent_arrears (council_tax_id NUMBER, cmi_cross_ref_id NUMBER)
CREATE TABLE electoral_register (electoral_register_id NUMBER, cmi_cross_ref_id NUMBER)
CREATE TABLE customer_master_index (master_customer_id NUMBER, cmi_details CLOB)
CREATE TABLE council_tax (council_tax_id NUMBER, cmi_cross_ref_id NUMBER)

Which distinct source system code includes the substring 'en'?
SELECT DISTINCT source_system_code FROM cmi_cross_references WHERE source_system_code LIKE '%en%'
SELECT DISTINCT "source_system_code" FROM "cmi_cross_references" WHERE "source_system_code" LIKE '%en%'