Question

I’ve been stuck on a query where there is a CUSTOMER and a PHONE table.

It is a one to many relationship, in which a CUSTOMER and have many PHONE numbers

The table is like the following:

---CUSTOMER---
cust_ID
cust_Name

---PHONE---
cust_ID
Phone_type (M or O for mobile/office respectively)
phone_no

I want to write a query where the output would be similar to the following:

cust_name | M_Phone | O_Phone

Where the M_Phone is the mobile number and the O_Phone is the office number.

Answer 1

select C.cust_Name,
       PM.phone_no as M_Phone,
       PO.phone_no as O_Phone
from CUSTOMER as C
  left outer join @PHONE as PM
    on C.cust_ID = PM.cust_ID and
       PM.phone_no = 'M'
  left outer join PHONE as PO
    on C.cust_ID = PO.cust_ID and
       PO.phone_no = 'O'

The above query will give you customers without any phone numbers as well.
If you only want customer that actually have a phone add this where clause.

where PM.phone_no is not null or
      PO.phone_no is not null