用MySQL GROUP BY按组列出所有行？
要按组列出所有行，可以使用GROUP_CONCAT()。让我们首先创建一个表-
create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Name varchar(20), Value varchar(100) );
使用插入命令在表中插入一些记录-
insert into DemoTable(Name,Value) values('John','John');
insert into DemoTable(Name,Value) values('Carol','Carol');
insert into DemoTable(Name,Value) values('John','Works');
insert into DemoTable(Name,Value) values('Carol','Works');
insert into DemoTable(Name,Value) values('John','At');
insert into DemoTable(Name,Value) values('Carol','At');
insert into DemoTable(Name,Value) values('John','Amazon');
insert into DemoTable(Name,Value) values('Carol','Google');使用select语句显示表中的所有记录-
select *from DemoTable;
这将产生以下输出-
+----+-------+--------+ | Id | Name | Value | +----+-------+--------+ | 1 | John | John | | 2 | Carol | Carol | | 3 | John | Works | | 4 | Carol | Works | | 5 | John | At | | 6 | Carol | At | | 7 | John | Amazon | | 8 | Carol | Google | +----+-------+--------+ 8 rows in set (0.00 sec)
以下是按组列出所有行的查询。在这里，将获取“John”的值，即“John在id，3、5、7的Amazon工作。”同样，它也适用于“Carol”-
select Name, GROUP_CONCAT(Value SEPARATOR ' ') AS `Complete_Status` from DemoTable group by Name;
这将产生以下输出-
+-------+-----------------------+ | Name | Complete_Status | +-------+-----------------------+ | Carol | Carol Works At Google | | John | John Works At Amazon | +-------+-----------------------+ 2 rows in set (0.00 sec)