MySQL GROUP_CONCAT()的使用
1. MySQL GROUP_CONCAT()
mysql> SELECT pub_id,GROUP_CONCAT(cate_id) -> FROM book_mast -> GROUP BY pub_id;
返回結果:(默認逗號分隔)
+--------+-----------------------+
| pub_id | GROUP_CONCAT(cate_id) |
+--------+-----------------------+
| P001 | CA002,CA004 |
| P002 | CA003,CA003 |
| P003 | CA001,CA003 |
| P004 | CA005,CA002 |
| P005 | CA001,CA004 |
| P006 | CA005,CA001 |
| P007 | CA005,CA002 |
| P008 | CA005,CA004 |
+--------+-----------------------+
2.MySQL GROUP_CONCAT() with order by and distinct
語句:(DISTINCT:消重,看結果的第四行CA003,只有一個。ASC:升序)
mysql> SELECT pub_id,GROUP_CONCAT(DISTINCT cate_id) -> FROM book_mast -> GROUP BY pub_id -> ORDER BY GROUP_CONCAT(DISTINCT cate_id) ASC;
返回結果:
+--------+--------------------------------+
| pub_id | GROUP_CONCAT(DISTINCT cate_id) |
+--------+--------------------------------+
| P003 | CA001,CA003 |
| P005 | CA001,CA004 |
| P001 | CA002,CA004 |
| P002 | CA003 |
| P006 | CA005,CA001 |
| P004 | CA005,CA002 |
| P007 | CA005,CA002 |
| P008 | CA005,CA004 |
+--------+--------------------------------
3. MySQL GROUP_CONCAT() with separator
語句: mysql> SELECT pub_id,GROUP_CONCAT(DISTINCT cate_id -> ORDER BY cate_id ASC SEPARATOR ‘ ‘) --去除逗號 -> FROM book_mast -> GROUP BY pub_id ;
+--------+----------------
返回結果:
+--------+--------------------------------------------------------------------+
| pub_id | GROUP_CONCAT(DISTINCT cate_id ORDER BY cate_id ASC SEPARATOR ‘ ‘) |
+--------+--------------------------------------------------------------------+
| P001 | CA002 CA004 |
| P002 | CA003 |
| P003 | CA001 CA003 |
| P004 | CA002 CA005 |
| P005 | CA001 CA004 |
| P006 | CA001 CA005 |
| P007 | CA002 CA005 |
| P008 | CA004 CA005 |
+--------+--------------------------------------------------------------------+
參考文章:http://www.w3resource.com/mysql/aggregate-functions-and-grouping/aggregate-functions-and-grouping-group_concat.php#
MySQL GROUP_CONCAT()的使用