按 Id 分組並連線 MySQL 查詢？

我們先建立一個表 -

mysql> create table DemoTable
(
   Id int,
   Name varchar(100)
);
Query OK, 0 rows affected (0.64 sec)

使用 insert 命令向表中插入一些記錄 -

mysql> insert into DemoTable values(100,'Chris');
Query OK, 1 row affected (0.44 sec)
mysql> insert into DemoTable values(200,'Robert');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values(100,'Chris');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable values(300,'David');
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable values(400,'Mike');
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable values(400,'Mike');
Query OK, 1 row affected (0.10 sec)

使用 select 語句從表中顯示所有記錄 -

mysql> select *from DemoTable;

這將生成以下輸出 -

+------+--------+
| Id   | Name   |
+------+--------+
|  100 | Chris  |
|  200 | Robert |
|  100 | Chris  |
|  300 | David  |
|  400 | Mike   |
|  400 | Mike   |
+------+--------+
6 rows in set (0.00 sec)

以下是將 MySQL group Concat 按 Id 分組的查詢 -

mysql> select group_concat(Name)
from
(
   select distinct Id,Name from DemoTable
)
tbl;

這將生成以下輸出 -

+-------------------------+
| group_concat(Name)      |
+-------------------------+
| Chris,Robert,David,Mike |
+-------------------------+
1 row in set (0.00 sec)

AmitDiwan

更新日期:26-9-2019

402 次瀏覽

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