Question

我得到的查询工作正常：

SELECT Course, Period, Room, Location, TeacherId, GROUP_CONCAT(StudentId) as Students 
FROM cursosv2 
GROUP BY Course, Period, Room, Location, TeacherID;

我想要的（可能太基本）是在结果查询中有一个新列，例如NEW COLUMN A，其中包含句点+ room +'final'的连接值。但我一直在例外。不知道真正的原因。

我在尝试什么...

SELECT Course, Period, Room, Period+' '+Room+' Final' as test, Location, TeacherId, GROUP_CONCAT(StudentId) as Students 
FROM cursosv2 
GROUP BY Course, Period, Room, Location, TeacherID;

感谢。

Answer 1

您还应该使用concat进行字符串连接（而非+）并添加到

组

{{1}}

Answer 2

您可以使用CONCAT_WS来实现这一目标。

（＆＃39;＆＃39;，Column1，column2）AS column_name

SELECT Course, Period, Room, concat_ws(' ', Room, Period) AS roomperiod, Location, TeacherId, GROUP_CONCAT(StudentId) as Students FROM cursosv2 GROUP BY Course, Period, Room, Location, TeacherID;

https://dev.mysql.com/doc/refman/5.5/en/string-functions.html#function_concat-ws

Answer 3

使用concat连接而不是+。并将test添加到group by子句：

SELECT Course, Period, Room, concat(Period,' ',Room,' Final') as test, 
       Location, TeacherId, GROUP_CONCAT(StudentId) as Students 
FROM cursosv2 
GROUP BY Course, Period, Room, test, Location, TeacherID;

添加了列的Group_concat

3 个答案: