从 MySQL 中提取数据以使其格式化为重复值的最有效方法是什么
mysqlmysqli database更新于 2024/2/4 2:42:00
为此，您可以使用 GROUP_CONCAT()。让我们首先创建一个表 −
mysql> create table DemoTable1561 -> ( -> StudentName varchar(20), -> Title text -> ); Query OK, 0 rows affected (0.60 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable1561 values('Adam','Learning Java');
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable1561 values('Bob','Learning C');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1561 values('Adam','Learning Spring and Hibernate Framework');
Query OK, 1 row affected (0.22 sec)
mysql> insert into DemoTable1561 values('Carol','Learning MySQL from basic');
Query OK, 1 row affected (0.30 sec)
使用 select 语句显示表中的所有记录 −
mysql> select * from DemoTable1561;
这将产生以下输出 −
+-------------+-----------------------------------------+ | StudentName | Title | +-------------+-----------------------------------------+ | Adam | Learning Java | | Bob | Learning C | | Adam | Learning Spring and Hibernare Framework | | Carol | Learning MySQL from basic | +-------------+-----------------------------------------+ 4 rows in set (0.00 sec)
这是从 MySQL 中提取数据以便格式化的查询 −
mysql> select StudentName,group_concat(Title separator ',') as FormattedOutput from DemoTable1561 -> group by StudentName;
这将产生以下输出 −
+-------------+-------------------------------------------------------+ | StudentName | FormattedOutput | +-------------+-------------------------------------------------------+ | Adam | Learning Java,Learning Spring and Hibernate Framework | | Bob | Learning C | | Carol | Learning MySQL from basic | +-------------+-------------------------------------------------------+ 3 rows in set (0.00 sec)
