SQL split values to multiple rows

If you can create a numbers table, that contains numbers from 1 to the maximum fields to split, you could use a solution like this:

select  tablename.id,  SUBSTRING_INDEX(SUBSTRING_INDEX(tablename.name, ',', numbers.n), ',', -1) namefrom  numbers inner join tablename  on CHAR_LENGTH(tablename.name)     -CHAR_LENGTH(REPLACE(tablename.name, ',', ''))>=numbers.n-1order by  id, n

Please see fiddle here.

If you cannot create a table, then a solution can be this:

select  tablename.id,  SUBSTRING_INDEX(SUBSTRING_INDEX(tablename.name, ',', numbers.n), ',', -1) namefrom  (select 1 n union all   select 2 union all select 3 union all   select 4 union all select 5) numbers INNER JOIN tablename  on CHAR_LENGTH(tablename.name)     -CHAR_LENGTH(REPLACE(tablename.name, ',', ''))>=numbers.n-1order by  id, n

an example fiddle is here.

If the name column were a JSON array (like '["a","b","c"]'), then you could extract/unpack it with JSON_TABLE() (available since MySQL 8.0.4):

select t.id, j.namefrom mytable tjoin json_table(  t.name,  '$[*]' columns (name varchar(50) path '$')) j;

Result:

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

View on DB Fiddle

If you store the values in a simple CSV format, then you would first need to convert it to JSON:

select t.id, j.namefrom mytable tjoin json_table(  replace(json_array(t.name), ',', '","'),  '$[*]' columns (name varchar(50) path '$')) j

Result:

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

View on DB Fiddle

I have take the reference from here with changed column name.

DELIMITER $$CREATE FUNCTION strSplit(x VARCHAR(65000), delim VARCHAR(12), pos INTEGER) RETURNS VARCHAR(65000)BEGIN  DECLARE output VARCHAR(65000);  SET output = REPLACE(SUBSTRING(SUBSTRING_INDEX(x, delim, pos)                 , LENGTH(SUBSTRING_INDEX(x, delim, pos - 1)) + 1)                 , delim                 , '');  IF output = '' THEN SET output = null; END IF;  RETURN output;END $$CREATE PROCEDURE BadTableToGoodTable()BEGIN  DECLARE i INTEGER;  SET i = 1;  REPEAT    INSERT INTO GoodTable (id, name)      SELECT id, strSplit(name, ',', i) FROM BadTable      WHERE strSplit(name, ',', i) IS NOT NULL;    SET i = i + 1;    UNTIL ROW_COUNT() = 0  END REPEAT;END $$DELIMITER ;