select
@first:=SUBSTRING_INDEX(combinations,',',1) as first,
@second:=substring_index(SUBSTRING_INDEX(combinations,',',2), ',', -1) as second,
@third:=substring_index(SUBSTRING_INDEX(combinations,',',3), ',', -1) as third,
@forth:=substring_index(SUBSTRING_INDEX(combinations,',',4), ',', -1) as forth,
@fifth:=substring_index(SUBSTRING_INDEX(combinations,',',5), ',', -1) as fifth,
@sixth:=SUBSTRING_INDEX(combinations,',',-1) as sixth,
@suma:=@first+@second+@third+@forth+@fifth+@sixth as suma
from All_combinations limit 10;

+-------+--------+-------+-------+-------+-------+------+
| first | second | third | forth | fifth | sixth | suma |
+-------+--------+-------+-------+-------+-------+------+
| 1     | 2      | 3     | 4     | 5     | 6     |   21 |
| 1     | 2      | 3     | 4     | 5     | 7     |   22 |
| 1     | 2      | 3     | 4     | 5     | 8     |   23 |
| 1     | 2      | 3     | 4     | 5     | 9     |   24 |
| 1     | 2      | 3     | 4     | 5     | 10    |   25 |
| 1     | 2      | 3     | 4     | 5     | 11    |   26 |
| 1     | 2      | 3     | 4     | 5     | 12    |   27 |
| 1     | 2      | 3     | 4     | 5     | 13    |   28 |
| 1     | 2      | 3     | 4     | 5     | 14    |   29 |
| 1     | 2      | 3     | 4     | 5     | 15    |   30 |
+-------+--------+-------+-------+-------+-------+------+
10 rows in set (0.00 sec)