How to calculate percentage of each row in SQL Server 2012?

Question

I have a table in SQL Server 2012 with data like this:

Request_Type    Total_Count
---------------------------
   General         25
   Inquiry         15

I want to return the percentage of counts in the last column like this:

Request_Type    Total_Count    Total_Percentage
--------------------------------------------------
   General         25              62.5
   Inquiry         15              37.5

I tried the following query,

select 
    Request_Type, Total_Count, 
    (Total_Count* 100) / isnull(sum(Total_Count),0) as Total_Percentage 
from 
    tbl_Request

but it returns 100 in the Total_Percentage column.

Any ideas on how to achieve the result will be appreciated.

Thanks.

Answer 1

You can use subquery to get the SUM(Total_Count):

SELECT Request_Type
     , Total_Count
     , (Total_Count * 100) / (SELECT SUM(Total_Count) FROM tbl_Request) AS Total_Percentage
FROM tbl_Request

Answer 2

Use Sum Over() trick to get the sum of all the rows then find the percentage. Try this..

SELECT Request_Type,
       Total_Count,
       ( Total_Count * 100.0 ) / Sum(Total_Count)OVER()
FROM  (SELECT 'General' AS Request_Type,25        AS Total_Count
       UNION
       SELECT 'Inquiry',15)a 

Result:

Request_Type    Total_Count Percentage
General         25          62.5
Inquiry         15          37.5