组连接MySQL列中的姓氏，并设置条件以显示有限的记录
使用GROUP_CONCAT()执行组串联并设置条件。让我们首先创建一个表-
mysql> create table DemoTable813( UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserFirstName varchar(100), UserLastName varchar(100) );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable813(UserFirstName,UserLastName) values('Adam','Smith');
mysql> insert into DemoTable813(UserFirstName,UserLastName) values('Chris','Brown');
mysql> insert into DemoTable813(UserFirstName,UserLastName) values('David','Miller');
mysql> insert into DemoTable813(UserFirstName,UserLastName) values('Carol','Taylor');使用select语句显示表中的所有记录-
mysql> select *from DemoTable813;
这将产生以下输出-
+--------+---------------+--------------+ | UserId | UserFirstName | UserLastName | +--------+---------------+--------------+ | 1 | Adam | Smith | | 2 | Chris | Brown | | 3 | David | Miller | | 4 | Carol | Taylor | +--------+---------------+--------------+ 4 rows in set (0.00 sec)
以下是如何分组连接并仅显示姓氏-
mysql> select group_concat(UserLastName) from DemoTable813 where UserId < 4;
这将产生以下输出-
+----------------------------+ | group_concat(UserLastName) | +----------------------------+ | Smith,Brown,Miller | +----------------------------+ 1 row in set (0.00 sec)