Try using an aggregate function (such as MAX) for each of the columns like shown below. If you expect a different row for each customer, you would also need to group by customerid or a similar columnSELECT MAX(CASE
WHEN isMobile = 0 THEN Number
END) AS LandNumber,
MAX(CASE
WHEN isMobile = 0 THEN AreaCode
END) AS LandAreaCode,
MAX(CASE
WHEN isMobile = 0 THEN CountryCodeID
END) AS LandCountryCode,
MAX(CASE
WHEN isMobile = 1 THEN (Number)
END) AS MobileNumber,
MAX(CASE
WHEN isMobile = 1 THEN CountryCodeID
END) AS MobileCountryCode
FROM Cust_ContactNumbers
WHERE Cust_Family_ID = 150