Preface:
There is such a table (product), statistical classification needs to be done
| id | name | on one | type |
| 1 | apple | 1 | fruit |
| 2 | pear | 2 | fruit |
| 3 | watermelon | 4 | fruit |
| 4 | book | 1 | stationery |
| 5 | pencil | 3 | stationery |
text:
1, need to be classified according to type
aims:
| fruit | Apples, pears, watermelon |
| stationery | Book, pencil |
Statement:
select type, wm_concat(name) name from product group by type
2, classified by type, and obtains a corresponding number of
aims:
| fruit | Apple (1), pears (2), watermelon (4) |
| stationery | Book (1), a pencil (3) |
Statement:
select type, wm_concat(name || '(' || num || ')') name from product group by type
Reference blog:
Oracle wm_concat () function - light rain cold - blog Park
https://www.cnblogs.com/qianyuliang/p/6649983.html