SQLite中的Case语句给出错误的结果

当我在SQLite中的表上打印结果时，输出如下

SELECT Protocol, case (Protocol) 
When TYPE = 1 then 'Peer' 
When TYPE = 2 then 'TCMP' 
When TYPE = 3 then 'ICMP' 
When TYPE = 4 then 'Jitter'
ELSE 'Unknown'
END as Name

From 
(
select 
Protocol from ProtocolDetails group by Protocol 
) 
as T

我的问题是为什么3号和4号打印了Unknown，我的案例陈述有什么问题吗？

你是在混音。尝试：

您的布尔表达式将作为数字计算

Protocol     Name

1            Peer
3            Unknown
4            Unknown

SELECT Protocol,
       (case When TYPE = 1 then 'Peer' 
             When TYPE = 2 then 'TCMP' 
             When TYPE = 3 then 'ICMP' 
             When TYPE = 4 then 'Jitter'
             else 'Unknown'
        end) as Name
From (select Protocol
      from ProtocolDetails
      group by Protocol 
     ) T;