SQL Conditional Case

Question

I have a table that lists items and a status about these items. The problem is that some items have multiple different status entries. For example.

HOST          Status
1.1.1.1       PASS
1.1.1.1       FAIL
1.2.2.2       FAIL
1.2.3.3       PASS
1.4.2.1       FAIL
1.4.2.1       FAIL
1.1.4.4       NULL

I need to return one status per asset.

HOST          Status
1.1.1.1       PASS
1.2.2.2       FAIL
1.2.3.3       PASS
1.4.2.1       FAIL
1.1.4.4         No Results

I have been trying to do this with T-SQL Case statements but can't quite get it right. The conditions are any Pass + anything is a Pass, Fail+ No Results is a fail and Null is No Results.

Answer 1

Try using a case statement to convert to ordered results and group on that, finally, you'll need to convert back to the nice, human-readable answer:

with cte1 as (
  SELECT HOST,
         [statNum] = case
                      when Status like 'PASS' then 2
                      when Status like 'FAIL' then 1
                      else 0
                    end
  FROM table
)
SELECT HOST, case max(statNum) when 2 then 'PASS' when 1 then 'FAIL' else 'No Results' end
FROM cte1
GROUP BY HOST

NOTE: I used a CTE statement to hopefully make things a little clearer, but everything could be done in a single SELECT, like so:

SELECT HOST,
 [Status] = case max(case when Status like 'PASS' then 2 when Status like 'FAIL' then 1 else 0 end)
    when 2 then 'PASS'
    when 1 then 'FAIL'
    else 'No Result'
   end
FROM table

Answer 2

You can use Max(Status) with Group by Host to get Distinct values:

Select host, coalesce(Max(status),'No results') status
From Table1
Group by host
Order by host

Fiddle Demo Results:

|    HOST |     STATUS |
|---------|------------|
| 1.1.1.1 |       PASS |
| 1.1.4.4 | No results |
| 1.2.2.2 |       FAIL |
| 1.2.3.3 |       PASS |
| 1.4.2.1 |       FAIL |

By default SQL Server is case insensitive, If case sensitivity is a concern for your server, then use the lower() function as below:

Select host, coalesce(Max(Lower(status)),'No results') status
From Table1
Group by host
Order by host

Fiddle demo

Answer 3

WITH CTE( HOST, STATUSValue)
AS(
     SELECT HOST,
     CASE STATUS WHEN 'PASS' 1 ELSE 0 END AS StatusValue
     FROM Data
)

SELECT DISTINCT HOST,
  CASE ISNULL(GOOD.STATUSVALUE,-1) WHEN 1 THEN 'Pass' 
       ELSE CASE ISNULL( BAD.STATUSVALUE,-1) WHEN 0 Then 'Fail' Else 'No Results' END
  END AS Results
FROM DATA AS D
LEFT JOIN CTE AS GOOD
  ON GOOD.HOST = D.HOST
 AND GOOD.STATUSVALUE = 1
LEFT JOIN CTE AS BAD
  ON BAD.HOST = BAD.HOST
 AND BAD.STATUSVALUE = 0