Split a string into rows using pure SQLite

Question

Using SQLite, I\'d like to split a string in the following way.

Input string:

C:\\Users\\fidel\\Desktop\\Temp

and have

Answer 1

Recursive CTE:

WITH RECURSIVE cte(org, part, rest, pos) AS (
  VALUES('C:\Users\fidel\Desktop\Temp', '','C:\Users\fidel\Desktop\Temp'|| '\', 0)
  UNION ALL
  SELECT org,
         SUBSTR(org,1, pos + INSTR(rest, '\')),
         SUBSTR(rest, INSTR(rest, '\')+1),
         pos + INSTR(rest, '\')
  FROM cte
  WHERE INSTR(rest, '\') > 0                         
)
SELECT *
FROM cte
WHERE pos <> 0
ORDER BY pos; 

SqlFiddleDemo

Output:

╔═════════════════════════════╗
║            part             ║
╠═════════════════════════════╣
║ C:\                         ║
║ C:\Users\                   ║
║ C:\Users\fidel\             ║
║ C:\Users\fidel\Desktop\     ║
║ C:\Users\fidel\Desktop\Temp ║
╚═════════════════════════════╝

How it works:

org  - original string does not change
part - simply `LEFT` equivalent of original string taking pos number of chars
rest - simply `RIGHT` equivalent, rest of org string
pos  - position of first `\` in the rest 

Trace:

╔══════════════════════════════╦══════════════════════════════╦════════════════════════════╦═════╗
║             org              ║            part              ║           rest             ║ pos ║
╠══════════════════════════════╬══════════════════════════════╬════════════════════════════╬═════╣
║ C:\Users\fidel\Desktop\Temp  ║ C:\                          ║ Users\fidel\Desktop\Temp\  ║   3 ║
║ C:\Users\fidel\Desktop\Temp  ║ C:\Users\                    ║ fidel\Desktop\Temp\        ║   9 ║
║ C:\Users\fidel\Desktop\Temp  ║ C:\Users\fidel\              ║ Desktop\Temp\              ║  15 ║
║ C:\Users\fidel\Desktop\Temp  ║ C:\Users\fidel\Desktop\      ║ Temp\                      ║  23 ║
║ C:\Users\fidel\Desktop\Temp  ║ C:\Users\fidel\Desktop\Temp  ║                            ║  28 ║
╚══════════════════════════════╩══════════════════════════════╩════════════════════════════╩═════╝

Answer 2

If you want to search for the values ​​individually, use the code below:

WITH RECURSIVE split(content, last, rest) AS (
VALUES('', '', 'value1§value2§value3§value4§value5§value6§value7')
UNION ALL
  SELECT 

    CASE WHEN last = '§' 
            THEN
                substr(rest, 1, 1)
            ELSE
                content || substr(rest, 1, 1)
    END,
     substr(rest, 1, 1),
     substr(rest, 2)
  FROM split
  WHERE rest <> ''
)
SELECT 
       REPLACE(content, '§','') AS 'ValueSplit'     
FROM 
       split
WHERE 
       last = '§' OR rest ='';

Result:

**ValueSplit**

value1
value2
value3
value4
value5
value6
value7

I hope I can help people with the same problem.

Answer 3

This is possible with a recursive common table expression:

WITH RECURSIVE split(s, last, rest) AS (
  VALUES('', '', 'C:\Users\fidel\Desktop\Temp')
  UNION ALL
  SELECT s || substr(rest, 1, 1),
         substr(rest, 1, 1),
         substr(rest, 2)
  FROM split
  WHERE rest <> ''
)
SELECT s
FROM split
WHERE rest = ''
   OR last = '\';

^{(You did not ask for a reasonable way.)}

Answer 4

Inspired from Lukasz Szozda's answer:

 WITH RECURSIVE cte("pre","post") AS (   
   VALUES('C:', 'Users\fidel\Desktop\Temp' || '\')
 UNION ALL
   SELECT "pre" || '\' || left("post",     position('\' in "post")-1),
                     substring("post" from position('\' in "post")+1)
   FROM cte   
   WHERE "post" > ''                             
 ) 
 SELECT "pre" FROM cte

(tested on PostgreSQL)

The idea is now to replace the VALUES line

VALUES('C:', 'Users\fidel\Desktop\Temp' || '\')

with placeholders like

 VALUES(?, ? || '\')

which have been pre-split in the programming language that is going to run the SQL statement above against the data base.

Reading the SQLite docs, I see that substring(... from ...) has to be replaced by substr(..., ...) and position(... in ...) is to be replaced by instr(..., ...) with parameters swapped.

Very annoying for me since I wanted SQL code that runs on both PostgreSQL and SQLite.