求和函数中case语句中的SQL语法错误

Question

下面是我的代码：

SELECT HOUR(asl.Start_Time) AS [Hour],
       t.team_name,
       SUM( CASE WHEN asl.Working = 1 
                 THEN asl.Duration_Seconds 
                 ELSE 0 END) 
           AS TotalSeconds
FROM (Agents 
         INNER JOIN Teams AS t 
         ON Agents.team_no = Teams.team_no)
      INNER JOIN AgentStateLogs AS asl 
      ON Agents.agent_no = asl.Agent_No
GROUP BY t.team_name, HOUR(asl.Start_Time);

问题是它说声明中缺少一个操作符：

SUM( CASE WHEN asl.Working = 1 
          THEN asl.Duration_Seconds 
          ELSE 0 END) 
    AS TotalSeconds

我一直在找它，我只是看不出错误在哪里。有人能帮我弄清楚这件事吗？这一代码正在MS Access 2013中完成。

提前谢谢你。

Answer 1

CASE WHEN asl.Working = 1 
THEN asl.Duration_Seconds 
ELSE 0 END

翻译成JET，这会变成

IIf(asl.Working = 1, asl.Duration_Seconds, 0)

在手册中搜索即时if以获得更多信息。