SQL split comma separated row [duplicate] - mysql

Question

This question already has answers here:
MySQL: Split comma separated list into multiple rows
(4 answers)
Closed 9 years ago.
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