This is my table:
id | fk_company ------------------- 1 | 2 2 | 2 3 | 2 4 | 4 5 | 4 6 | 11
You need to COUNT() with GROUP BY in an inner SELECT clause first and then apply GROUP_CONCAT();
COUNT()
GROUP BY
SELECT
GROUP_CONCAT()
SELECT GROUP_CONCAT(cnt) cnt FROM ( SELECT COUNT(*) cnt FROM table1 GROUP BY fk_company ) q;
Output:
| CNT | ----------- | 3,2,3,1 |
Here is SQLFiddle demo.