按列值对数组中的 MySQL 行进行分组?
mysqlmysqli database
要对数组中的行进行分组，请使用 GROUP_CONCAT() 和 ORDER BY 子句。让我们首先创建一个表 −
mysql> create table DemoTable -> ( -> Id int, -> FirstName varchar(20) -> ); Query OK, 0 rows affected (0.78 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable values(101,'John'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(102,'Bob'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values(101,'David'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values(101,'Adam'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(102,'Chris'); Query OK, 1 row affected (0.15 sec)
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable;
这将产生以下输出 −
+------+-----------+ | Id | FirstName | +------+-----------+ | 101 | John | | 102 | Bob | | 101 | David | | 101 | Adam | | 102 | Chris | +------+-----------+ 5 rows in set (0.00 sec)
以下是按列值对数组中的 MySQL 行进行分组的查询 −
mysql> select Id,group_concat(FirstName separator ',') from DemoTable -> group by Id -> order by count(Id);
这将产生以下输出 −
+------+---------------------------------------+ | Id | group_concat(FirstName separator ',') | +------+---------------------------------------+ | 102 | Bob,Chris | | 101 | John,David,Adam | +------+---------------------------------------+ 2 rows in set (0.00 sec)
