Split values in parts with sqlite

Question

I\'m struggling to convert

a | a1,a2,a3
b | b1,b3
c | c2,c1

to:

Answer 1

Yes, a recursive common table expression is the solution:

with x(one, firstone, rest) as 
(select one, substr(many, 1, instr(many, ',')-1) as firstone, substr(many, instr(many, ',')+1) as rest from data where many like "%,%"
   UNION ALL
 select one, substr(rest, 1, instr(rest, ',')-1) as firstone, substr(rest, instr(rest, ',')+1) as rest from x    where rest like "%,%" LIMIT 200
)
select one, firstone from x UNION ALL select one, rest from x where rest not like "%,%" 
ORDER by one;

Output:

a|a1
a|a2
a|a3
b|b1
b|b3
c|c2
c|c1

Answer 2

Check my answer in How to split comma-separated value in SQLite?. This will give you the transformation in a single query rather than having to apply to each row.

-- using your data table assuming that b3 is suppose to be b2

WITH split(one, many, str) AS (
    SELECT one, '', many||',' FROM data
    UNION ALL SELECT one,
    substr(str, 0, instr(str, ',')),
    substr(str, instr(str, ',')+1)
    FROM split WHERE str !=''
) SELECT one, many FROM split WHERE many!='' ORDER BY one;

a|a1
a|a2
a|a3
b|b1
b|b2
c|c2
c|c1