Nối kết quả DISTINCT MySQL thành chuỗi

Sử dụng hàm GROUP_CONCAT(). Tạo bảng:

mysql> create table DemoTable    -> (    -> Subject varchar(10)    -> ); Query OK, 0 rows affected (0.43 sec)

Chèn dữ liệu:

mysql> insert into DemoTable values('C'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('C++'); Query OK, 1 row affected (0.25 sec) mysql> insert into DemoTable values('C++'); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable values('MongoDB'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('MySQL'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('MongoDB'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('MongoDB'); Query OK, 1 row affected (0.34 sec) mysql> insert into DemoTable values('Java'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('Java'); Query OK, 1 row affected (0.10 sec)

Hiển thị dữ liệu:

mysql> select *from DemoTable;

Kết quả

+---------+ | Subject | +---------+ | C       | | C++     | | C++     | | MongoDB | | MySQL   | | MongoDB | | MongoDB | | Java    | | Java    | +---------+ 9 rows in set (0.00 sec)

Truy vấn nối các giá trị distinct:

mysql> select group_concat(tbl.sub) from (select Subject sub from DemoTable group by Subject ) tbl;

Kết quả

+--------------------------+ | group_concat(tbl.sub)    | +--------------------------+ | C,C++,MongoDB,MySQL,Java | +--------------------------+ 1 row in set (0.04 sec)