mysql - SQL split comma separated row

Question

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Answer 1

You can do it with pure SQL like this

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(t.values, ',', n.n), ',', -1) value
  FROM table1 t CROSS JOIN 
(
   SELECT a.N + b.N * 10 + 1 n
     FROM 
    (SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) a
   ,(SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) b
    ORDER BY n
) n
 WHERE n.n <= 1 + (LENGTH(t.values) - LENGTH(REPLACE(t.values, ',', '')))
 ORDER BY value

Note: The trick is to leverage tally(numbers) table and a very handy in this case MySQL function SUBSTRING_INDEX(). If you do a lot of such queries (splitting) then you might consider to populate and use a persisted tally table instead of generating it on fly with a subquery like in this example. The subquery in this example generates a sequence of numbers from 1 to 100 effectively allowing you split up to 100 delimited values per row in source table. If you need more or less you can easily adjust it.

Output:

|          VALUE |
|----------------|
|     somethingA |
|     somethingB |
|     somethingC |
| somethingElseA |
| somethingElseB |

Here is SQLFiddle demo

---

This is how the query might look with a persisted tally table

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(t.values, ',', n.n), ',', -1) value
  FROM table1 t CROSS JOIN tally n
 WHERE n.n <= 1 + (LENGTH(t.values) - LENGTH(REPLACE(t.values, ',', '')))
 ORDER BY value

Here is SQLFiddle demo