Databasefletningstabeller

En mulig løsning ville være først at oprette en forespørgsel for hver type reservation (som du måske allerede har) og tilføje cust_type der og derefter forene de to sammen. Så de indledende forespørgsler ville være noget i stil med:

gæstereservationer:

SELECT reservation.r_id, guest.name, "guest" AS cust_type, {other fields}
FROM guest, reservation INNER JOIN guest ON guest.g_id = reservation.g_id;

company_reservations:

SELECT reservation.r_id, company.name, "company" AS cust_type {other fields}
FROM company, reservation INNER JOIN company ON company.c_id = reservation.c_id;

Så kan du forene de to forespørgsler sammen, noget som nedenfor.

SELECT reservation.r_id, guest.name, "guest" AS cust_type, {other fields}
FROM guest, reservation INNER JOIN guest ON guest.g_id = reservation.g_id
UNION SELECT reservation.r_id, company.name, "company" AS cust_type {other fields}
FROM company, reservation INNER JOIN company ON company.c_id = reservation.c_id;

Husk selvfølgelig enten at fjerne {other fields} eller tilføje hvad du ellers har brug for der.