Question

I am using SQL Server 2000. I am trying to calculate Net Promoter Score or NPS based on the below formula

Formula: (Promoters - Detractors) / Total Questions

• Scores 9 – 10 are considered promoters.
• Scores 0 – 6 are considered detractors.
• Scores 7 – 8 are considered neutral.

I have the following data:

Time           Q1      Q2      Q3
-----------  ------  ------  ------
2012-03-14      7       7       5
2012-03-15      3       2       5
2012-03-15      7      NA       2
2012-03-15      9      10     NULL
2012-03-15      8       4       4
2012-03-15     NA       6       4
2012-03-16      1       7       4
2012-03-16     NULL     0       5
2012-03-17      9       9       2
2012-03-19      0       0       1
2012-03-19      8       5       4
2012-03-19      1       0       3

The person who originally wrote the database stored NULL values as blanks or NA enter code herein a NVARCHAR format (only god knows why..) so the query I am playing with now uses a ISNUMERIC and im trying not to count blank or NA values.

My query, which doesnt work properly looks like:

 SELECT CAST(SUM(CASE WHEN ISNUMERIC([Q1]) != 1 THEN 0
             WHEN CAST([Q1] AS int) >= 9 THEN 1
             WHEN CAST([Q1] AS int) <= 6 THEN -1
             ELSE 0 END)
    + SUM(CASE WHEN ISNUMERIC([Q2]) != 1 THEN 0
             WHEN CAST([Q2] AS int) >= 9 THEN 1
             WHEN CAST([Q2] AS int) <= 6 THEN -1
             ELSE 0 END)
    + SUM(CASE WHEN ISNUMERIC([Q3]) != 1 THEN 0
             WHEN CAST([Q3] AS int) >= 9 THEN 1
             WHEN CAST([Q3] AS int) <= 6 THEN -1
             ELSE 0 END)
   AS FLOAT)
    / (SUM(CASE WHEN ISNUMERIC([Q1]) != 1 THEN 0
               ELSE 1 END)
    + SUM(CASE WHEN ISNUMERIC([Q2]) != 1 THEN 0
               ELSE 1 END)
    + SUM(CASE WHEN ISNUMERIC([Q3]) != 1 THEN 0
               ELSE 1 END)
   ) as [NPS]
FROM [nps]

Can someone point me in the right direction?
Thanks!

Answer 1

As others pointed out, changing the data type of the column from NVARCHAR to INT would be ideal.

Here is the query that might help you get the result that you need.

Click here to view the demo in SQL Fiddle using SQL Server 2012

Script:

SELECT  
        (
            SUM (CASE WHEN q >= 9 THEN 1.  END) -
            SUM (CASE WHEN q <= 6 THEN 1.  END)
        ) /
        SUM (1.) AS nps
FROM
(
        SELECT  (CASE   
                    WHEN ISNUMERIC(q1) <> 1 THEN 0. 
                    ELSE CAST(q1 AS FLOAT) 
                END) AS q   
        FROM [nps] 
    UNION ALL 
        SELECT  (CASE 
                    WHEN ISNUMERIC(q2) <> 1 THEN 0. 
                    ELSE CAST(q2 AS FLOAT) 
                END) AS q   
        FROM [nps] 
    UNION ALL 
        SELECT  (CASE 
                    WHEN ISNUMERIC(q3) <> 1 THEN 0. 
                    ELSE CAST(q3 AS FLOAT) 
                END) AS q   
        FROM [nps] 
) nps;

Output:

np
---------
-0.611111