SQL split values to multiple rows

Question

I have table :

id | name    
1  | a,b,c    
2  | b

i want output like this :

id | name    
1  | a    
1  | b    
1  | c             


        

Answer 1

The original question was for MySQL and SQL in general. The example below is for the new versions of MySQL. Unfortunately, a generic query that would work on any SQL server is not possible. Some servers do no support CTE, others do not have substring_index, yet others have built-in functions for splitting a string into multiple rows.

--- the answer follows ---

Recursive queries are convenient when the server does not provide built-in functionality. They can also be the bottleneck.

The following query was written and tested on MySQL version 8.0.16. It will not work on version 5.7-. The old versions do not support Common Table Expression (CTE) and thus recursive queries.

with recursive
  input as (
        select 1 as id, 'a,b,c' as names
      union
        select 2, 'b'
    ),
  recurs as (
        select id, 1 as pos, names as remain, substring_index( names, ',', 1 ) as name
          from input
      union all
        select id, pos + 1, substring( remain, char_length( name ) + 2 ),
            substring_index( substring( remain, char_length( name ) + 2 ), ',', 1 )
          from recurs
          where char_length( remain ) > char_length( name )
    )
select id, name
  from recurs
  order by id, pos;