SQL Server unpivot columns

Question

I have a table that I would like to unpivot in a SQL statement. It consists of a person and phone 1 through 5. Right now I'm doing a union for each phone but I fear it is causing performance issues.

Columns:

PERSON_GUID, 
PHONE_1, PHONE_1_VOICE_FLG, 
PHONE_2, PHONE_2_VOICE_FLG, 
PHONE_3, PHONE_3_VOICE_FLG, 
PHONE_4, PHONE_4_VOICE_FLG, 
PHONE_5, PHONE_5_VOICE_FLG

How would I best unpivot the row with performance in mind so that the results are:

PERSON_GUID, PHONE_NO, VOICE_FLG

Answer 1

I prefer UNPIVOT but as for your solution -
Make sure you are using UNION ALL and not UNION.
UNION ALL just spills one query result after the other.
UNION eliminates rows duplications and this is where you pay in performance.

---

select  PERSON_GUID,PHONE_NO,
        case right(col,1)
            when 1 then PHONE_1_VOICE_FLG
            when 2 then PHONE_2_VOICE_FLG
            when 3 then PHONE_3_VOICE_FLG
            when 4 then PHONE_4_VOICE_FLG
            when 5 then PHONE_5_VOICE_FLG
        end VOICE_FLG

from    t unpivot (PHONE_NO for col in
            (PHONE_1,PHONE_2,PHONE_3,PHONE_4,PHONE_5)) u