检查多个记录中的列值是否相同,并将这些记录设置在一行中,并在MySQL中用特殊字符分隔
为此,您可以将GROUP_CONCAT()与DISTINCT一起使用。让我们首先创建一个表-
mysql> create table DemoTable ( Id int, Subject varchar(40) );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable values(100,'MySQL'); mysql> insert into DemoTable values(100,'MongoDB'); mysql> insert into DemoTable values(100,'Java'); mysql> insert into DemoTable values(100,'MongoDB'); mysql> insert into DemoTable values(101,'MySQL'); mysql> insert into DemoTable values(101,'MySQL');
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 | Subject | +------+---------+ | 100 | MySQL | | 100 | MongoDB | | 100 | Java | | 100 | MongoDB | | 101 | MySQL | | 101 | MySQL | +------+---------+ 6 rows in set (0.00 sec)
以下是查询以检查多个记录之间的列值是否相同并将这些记录设置在由特殊字符分隔的单行中的查询。这里的分隔符是连字符-
mysql> select Id,group_concat(distinct Subject separator '-') as Subject from DemoTable group by Id;
这将产生以下输出-
+------+--------------------+ | Id | Subject | +------+--------------------+ | 100 | Java-MongoDB-MySQL | | 101 | MySQL | +------+--------------------+ 2 rows in set (0.04 sec)