Question

I have a table with a list of folders that looks like this:

Path                    Size
C:\ParentFolder\A       123
C:\ParentFolder\A\B     442434
C:\ParentFolder\A\B\C   13413412
C:\ParentFolder\D       2422341234
C:\ParentFolder\D\E     3342
C:\ParentFolder\D\E\F   2
C:\ParentFolder\D\E\G   2
...

I’m looking for some combination of SUM, GROUP BY, and PATINDEX/LTRIM/SUBSTRING/etc. which would give me back this:

Path                    SumSize
C:\ParentFolder\A       13855969
C:\ParentFolder\D       2422344580
...

C:\ParentFolder is a known prefix, but A,D,etc. are variable folder names. Do I need to write a function to accomplish that or can I use some combination of string functions?

Answer 1

Starting with your testing set,

CREATE TABLE #MyTable (Folder varchar(100) not null, Size bigint not null)

INSERT #MyTable values
  ('C:\ParentFolder\A'     ,  123)
 ,('C:\ParentFolder\A\B'   ,  442434)
 ,('C:\ParentFolder\A\B\C' ,  13413412)
 ,('C:\ParentFolder\D'     ,  2422341234)
 ,('C:\ParentFolder\D\E'   ,  3342)
 ,('C:\ParentFolder\D\E\F' ,  2)
 ,('C:\ParentFolder\D\E\G' ,  2)

you’d first determine what folders you want to summarize. I do so here by loading them into a temp table:

DECLARE @Targets table (Folder varchar(100) not null)
INSERT @Targets values
  ('C:\ParentFolder\A')
 ,('C:\ParentFolder\D')

From here it’s easy, using the like clause:

SELECT ta.Folder, sum(Size) TotalSize
 from @Targets ta
  left outer join #MyTable mt
   on mt.Folder like ta.Folder + '%'
 group by ta.Folder

Complications may ensue if your folders contain reserved characters used by the like clause: % _ ] [ and a few others.