SQL split comma separated row [duplicate]

Question

This question already has an answer here:

• MySQL: Split comma separated list into multiple rows 4 answers

I have a column with a variable number of comma seperated values:

somethingA,somethingB,somethingC
somethingElseA, somethingElseB

And I want the result to take each value, and create a row:

somethingA
somethingB
somethingC
somethingElseA
somethingElseB

How can I do this in SQL (MySQL)?

(I've tried googling "implode" and "lateral view", but those don't seem to turn up related questions. All the related SO questions are trying to do much more complicated things)

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