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法律研究如何在 MySQL 中连接字段？
要在 MySQL 中连接字段，可以使用 GROUP_CONCAT() 以及 GROUP BY。我们首先创建一个表格 -
mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentName varchar(30), StudentScore int ); Query OK, 0 rows affected (0.51 sec)
使用 insert 指令在表格中插入记录 -
mysql> insert into DemoTable( StudentName,StudentScore) values('Bob',80);
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable( StudentName,StudentScore) values('Bob',80);
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable( StudentName,StudentScore) values('Chris',90);
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable( StudentName,StudentScore) values('Chris',70);
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable( StudentName,StudentScore) values('Bob',50);
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable( StudentName,StudentScore) values('David',60);
Query OK, 1 row affected (0.23 sec)
mysql> insert into DemoTable( StudentName,StudentScore) values('Chris',99);
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable( StudentName,StudentScore) values('David',88);
Query OK, 1 row affected (0.18 sec)使用 select 语句在表格中显示所有记录 -
mysql> select * from DemoTable;
这将产生以下输出 -
+-----------+-------------+--------------+ | StudentId | StudentName | StudentScore | +-----------+-------------+--------------+ | 1 | Bob | 80 | | 2 | Bob | 80 | | 3 | Chris | 90 | | 4 | Chris | 70 | | 5 | Bob | 50 | | 6 | David | 60 | | 7 | Chris | 99 | | 8 | David | 88 | +-----------+-------------+--------------+ 8 rows in set (0.00 sec)
以下是在 MySQL 中连接字段的查询 -
mysql> select StudentName, group_concat(StudentScore separator ',') as Score from DemoTable group by StudentName;
这将产生以下输出 -
+-------------+----------+ | StudentName | Score | +-------------+----------+ | Bob | 80,80,50 | | Chris | 90,70,99 | | David | 60,88 | +-------------+----------+ 3 rows in set (0.24 sec)
更新于：2019-07-30
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