How to extract part of a string numerous times between delimiters and input into new columns T-SQL

Question

I want to extract part of a string numerous times from a value which has a number of the same delimiters and place the extracted strings into new columns.

Here is an example of the data I am working with (these folder paths could be even longer depending on the depth of the folder):

FolderPath:

Q:\downloads\extraction\bee\honey\
Q:\desktop\chocolate\london\time\spring\
Q:\documents\cars\astonmartin\vanquish\

I want to extract the whole string between delimiters from the left and place them into new columns at different stages of the string e.g.

FolderPath	RootDirectory	SubDirectory	SubSubDirectory
Q:\documents\cars\astonmartin\vanquish\	Q:\documents	Q:\documents\cars	Q:\documents\cars\astonmartin

I'm just wondering if this is possible, especially when folders names have all types of different lengths.

Any help would me much appreciated - thanks!

Answer 1

UPDATED (with a 2nd solution)

Solution #1 - Charindex + cascading APPLY:

--==== Sample Data
DECLARE @folders TABLE (Folder VARCHAR(1000));
INSERT  @folders VALUES
('Q:\downloads\extraction\bee\honey\'),
('Q:\desktop\chocolate\london\time\spring\'),
('Q:\documents\cars\astonmartin\vanquish\');

SELECT      FolderParse.*
FROM        @folders AS f
CROSS APPLY
(
  SELECT
    FolderPath      = f.Folder,
    RootDirectory   = SUBSTRING(f.Folder, 1, p2.Pos-2),
    SubDirectory    = SUBSTRING(f.Folder, 1, p3.Pos-1),
    SubSubDirectory = SUBSTRING(f.Folder, 1, p4.Pos-1)
  FROM        (VALUES(CHARINDEX('\',f.Folder)))          AS p1(Pos)
  CROSS APPLY (VALUES(CHARINDEX('\',f.Folder,p1.Pos+1))) AS p2(Pos)
  CROSS APPLY (VALUES(CHARINDEX('\',f.Folder,p2.Pos+1))) AS p3(Pos)
  CROSS APPLY (VALUES(CHARINDEX('\',f.Folder,p3.Pos+1))) AS p4(Pos)
) AS folderParse;

Results:

FolderPath                                RootDirectory  SubDirectory            SubSubDirectory
----------------------------------------- -------------- ----------------------- ---------------------------------
Q:\downloads\extraction\bee\honey\        Q:\downloads   Q:\downloads\extraction Q:\downloads\extraction\bee
Q:\desktop\chocolate\london\time\spring\  Q:\desktop     Q:\desktop\chocolate    Q:\desktop\chocolate\london
Q:\documents\cars\astonmartin\vanquish\   Q:\documents   Q:\documents\cars       Q:\documents\cars\astonmartin

Solution #2 - Tally Table:

The first solution is the way to go but this second one is better for when you need to go much deeper. For this you need to grab a copy of fnTally.

Here's how to do it against one string:

DECLARE @string VARCHAR(1000) =  'Q:\documents\cars\astonmartin\vanquish\';

SELECT
  FolderPath      = @string,
  RootDirectory   = MAX(CASE f.RN WHEN 1 THEN f.FPath END),
  SubDirectory    = MAX(CASE f.RN WHEN 2 THEN f.FPath END),
  SubSubDirectory = MAX(CASE f.RN WHEN 3 THEN f.FPath END)
FROM
(
  SELECT      ROW_NUMBER() OVER (ORDER BY t.N), SUBSTRING(@string,1,t.N+2)
  FROM        (VALUES(SUBSTRING(@string,4,1000))) AS s(Txt)
  CROSS APPLY dbo.fnTally(1,LEN(s.Txt))           AS t
  WHERE       SUBSTRING(s.Txt,t.N,1) = '\'
) AS f(RN,FPath);

Returns:

FolderPath                               RootDirectory      SubDirectory          SubSubDirectory
---------------------------------------- ------------------ --------------------- --------------------------------
Q:\documents\cars\astonmartin\vanquish\  Q:\documents       Q:\documents\cars     Q:\documents\cars\astonmartin

Against a table:

--==== Sample Data
DECLARE @folders TABLE (Folder VARCHAR(1000));
INSERT  @folders VALUES
('Q:\downloads\extraction\bee\honey\'),
('Q:\desktop\chocolate\london\time\spring\'),
('Q:\documents\cars\astonmartin\vanquish\');

--==== Solution
SELECT DirectoryParse.* 
FROM   @folders AS fld
CROSS APPLY
(
  SELECT
    FolderPath      = fld.Folder,
    RootDirectory   = MAX(CASE f.RN WHEN 1 THEN f.FPath END),
    SubDirectory    = MAX(CASE f.RN WHEN 2 THEN f.FPath END),
    SubSubDirectory = MAX(CASE f.RN WHEN 3 THEN f.FPath END)
  FROM
  (
    SELECT      ROW_NUMBER() OVER (ORDER BY t.N), SUBSTRING(fld.Folder,1,t.N+2)
    FROM        (VALUES(SUBSTRING(fld.Folder,4,1000))) AS s(Txt)
    CROSS APPLY dbo.fnTally(1,LEN(s.Txt))           AS t
    WHERE       SUBSTRING(s.Txt,t.N,1) = '\'
  ) AS f(RN,FPath)
) AS DirectoryParse;

Results:

FolderPath                                RootDirectory  SubDirectory            SubSubDirectory
----------------------------------------- -------------- ----------------------- ---------------------------------
Q:\downloads\extraction\bee\honey\        Q:\downloads   Q:\downloads\extraction Q:\downloads\extraction\bee
Q:\desktop\chocolate\london\time\spring\  Q:\desktop     Q:\desktop\chocolate    Q:\desktop\chocolate\london
Q:\documents\cars\astonmartin\vanquish\   Q:\documents   Q:\documents\cars       Q:\documents\cars\astonmartin