Question

I have a single table (Details) with fields “system” and “color_code”. I want to calculate the percent of items by color_code, for each system with a single SQL statement. I have this:

SELECT system, color_code, Count(color_code) AS ColorCount, 
       Count(color_code)*100 /(select count(*) from Detail) AS ColorPercent
FROM Detail
GROUP BY system, color_code;

The result in “ColorPercent” is of all records. I want the “ColorPercent” to be based on the number of records of each “system”.

I tried this (adding the “GROUP BY system” to the expression), but it doesn’t work,

SELECT system, color_code, Count(color_code) AS ColorCount, 
       Count(color_code)*100/(select count(*) from Detail 
                              GROUP BY system) AS ColorPercent
FROM Detail
GROUP BY system, color_code;

Answer 1

You need to restrict the records obtained in your sub-query.
Try:

SELECT system, color_code, Count(color_code) AS ColorCount, Count(color_code)*100 /(select count(*) from Detail where system = D.system) AS ColorPercent
FROM Detail D
GROUP BY system, color_code;

I’m not sure if you even need to alias your table or not