Select Distinct Values, Pass Into Where Clause

Question

I am trying to look at unique values in my table, and based on n number of values returned from the distinct query, pass those into a subsequent query in my WHERE clause.

Let me provide an example.

I have the a Table with the following columns:

ID | UserName | OtherCondition

I usually compute the total records, those which match a WHERE clause on OtherCondition , and their related percentages, as such:

SELECT 'Report' as ReportName,
COUNT(*) Match, 
(SELECT COUNT(*) FROM [MyTable) Total,
CAST(COUNT(*) AS FLOAT)/CAST((SELECT COUNT(*) FROM [MyTable]) AS FLOAT)*100 Percentage
FROM [MyTable]   
WHERE OtherCondition = MyCondition

Now, I am trying to integrate the UserName column into this query. By this I mean, what would happen is I look through the above table, and get all the unique usernames for all records (this can potentially be empty/null as well). This username would be passed into ReportName (currently a string literal) in the above (in the format of something like 'Report - ' [username]), and this would also be passed into a second WHERE condition. In totality, the WHERE condition would then look like:

WHERE OtherCondition = MyCondition AND UserName = [The Passed in unique username, from the not yet defined query]

Essentially, this would allow me to find all the unique users, and provide user based reporting.

Some sample data:

ID | UserName | OtherCondition
1    Mary         X
2    John         X
3    Mary         X

Expected Results:

 SELECT 'Report - Mary' as ReportName,
    COUNT(*) Match, 
    (SELECT COUNT(*) FROM [MyTable) Total,
    CAST(COUNT(*) AS FLOAT)/CAST((SELECT COUNT(*) FROM [MyTable]) AS FLOAT)*100 Percentage
    FROM [MyTable]   
    WHERE OtherCondition = x AND UserName = 'Mary'


 SELECT 'Report - John' as ReportName,
    COUNT(*) Match, 
    (SELECT COUNT(*) FROM [MyTable) Total,
    CAST(COUNT(*) AS FLOAT)/CAST((SELECT COUNT(*) FROM [MyTable]) AS FLOAT)*100 Percentage
    FROM [MyTable]   
    WHERE OtherCondition = x AND UserName = 'John'

Answer 1

It hope that I understood what you want:

SELECT ('Report - '+ UserName) as ReportName, 
       COUNT(*) Match, (SELECT COUNT(*) FROM [MyTable]) Total,
       CAST(COUNT(*) AS FLOAT) /
         CAST((SELECT COUNT(*) FROM [MyTable]) AS FLOAT)*100 Percentage
FROM [MyTable]   
WHERE OtherCondition = x
GROUP BY UserName;

This query delivers the output of the two last queries of your post.