CREATE VIEW purchase_due_by_purchase_id as SELECT ttl_sup_credit_by_id.supplier_id, ttl_sup_credit_by_id.ref, 
ttl_sup_credit_by_id.ttl_purchase, ttl_sup_debit_by_id.ttl_paid, (ttl_sup_credit_by_id.ttl_purchase-ttl_sup_debit_by_id.ttl_paid) as pur_due_by_pur_id FROM ttl_sup_credit_by_id LEFT JOIN ttl_sup_debit_by_id ON 
ttl_sup_credit_by_id.ref=ttl_sup_debit_by_id.ref;