如何获取从未完成的数据

Question

我的sql客户呼叫详细信息表中有一个数据，其中一个号码多次，有些第一次没有连接或下垂，但第二次连接，所以我只想获取从未连接过的数据

例： 这实际上是数据

Customer_Number        Status
123                    dropped
456                    connected
789                    dropped
123                    connected
456                    connected
789                    dropped
789                    not connected

我想得到这样的数据：

Customer_Number          Status
789                      dropped

Answer 1

它应该只显示那些从未连接的Customer_number。该查询连接每个客户编号的所有状态，并仅显示connection_status从未包含"已连接"的号码

select Customer_Number, group_concat(DISTINCT status) as connection_status 
from customers
GROUP BY Customer_Number
HAVING connection_status = 'dropped,not connected' OR connection_status='not connected,dropped'