I have a patient(Hospital) details stored in my database. The patient address details are stored in 2 tables. 1 for regular customers and other for 1 time customers. Table1 consists of amount charged to the patient.
If I understand the question correctly, you would LEFT JOIN table1 to table2 and table3 on p_no, then use the COALESCE() function on the address columns so that table2's columns are chosen when they are not NULL.