SQL SELECT with condition and unique name - sql

Question

Say I have the following table. If I want to return ONLY the inactive rows (Active = 0) but disregard a field that has the same FileName. For instance, the query should only return Helper0990329 since it is inactive and has no other filename in another row that is the same.
VinnyVincenzo1345090457296 should not be included in the results.
PATH | FileName | Active
C:\Vinny\ VinnyVincenzo1345090457296.mp3 0
C:\Vinny\ VinnyVincenzo1345090457296.mp3 1
C:\Vinny\ VinnyVincenzo1345137702505.mp3 1
C:\Helper\ Helper0990329.mp3 0
I tried the following but I ended up deactivating (and later deleting) files that I shoulnt have:
SELECT
[Path],
[FileName]
FROM [Flows].[dbo].[Flows_Flows]
Where [Active] = '0' AND [Created] > '8/18/2012'
Group By Path, FileName
Having count(FileName) = 1
GO

Answer 1

Assuming you are using SQL 2005 or greater, you can use ranking functions to solve this:
select *
from (SELECT [Path], [FileName],
count(*) over (partition by path, filename) as numFiles
FROM [Flows].[dbo].[Flows_Flows]
Where [Created] > '8/18/2012'
) t
where active = 0 and numfiles = 1
The problem with our query is that the WHERE clause was evaluated before the HAVING clause. So, the active rows were never seen.
Or, you can do this with a simple group by but a more complicated HAVING clause:
SELECT [Path], [FileName]
FROM [Flows].[dbo].[Flows_Flows]
Where [Created] > '8/18/2012'
Group By Path, FileName
Having count(FileName) = 1 and
sum(case when Active = '0' then 1 else 0 end) = 1

Answer 2

Try it by counting its number of instance inside SubQuery
SELECT [Path], [FileName]
FROM Flows_Flows a
INNER JOIN
(
SELECT [FileName],
COUNT([FileName]) TotalCount
FROM Flows_Flows
GROUP BY [FileName]
) b ON a.[FileName] = b.[FileName]
WHERE a.[Active] = 0 AND
a.[Created] > '8/18/2012' AND
b.TotalCount = 1

Answer 3

You can use a LEFT OUTER JOIN and when the join finds a duplicate row, exclude it (dup.path is null).
SELECT
f.[Path],
f.[FileName]
FROM [Flows].[dbo].[Flows_Flows] f
LEFT OUTER JOIN [Flows].[dbo].[Flows_Flows] dup on f.Path = dup.Path and dup.Active = '1' --Active must be set otherwise, we found ourselves
Where f.[Active] = '0' AND f.[Created] > '8/18/2012'
AND dup.Path is null -- here we exculde all rows that have a duplicate
The advantage being that this solution has no sub query nor aggregate. That being said, not having looked at the query plan, I cannot say if it is indeed faster. (I also just prefer this syntax, I suppose.)

Answer 4

I'm guessing you have an id field as well right?
I'm also assuming that you dont necessarily want only ones that aren't duplicate rather ones users that don't have ANY active entries.
You could use IN in the WHERE clause.
example:
SELECT Path, FileName FROM Flows_Flows WHERE Active = 0 AND id NOT IN
( SELECT id FROM Flows_Flows WHERE Active = 1 )