SELECT COUNT(*) AS "CNT",imei
FROM   devices

执行得很好.我想用WHERE语句进一步限制查询. (人性)逻辑下一步是随后修改查询：

SELECT COUNT(*) AS "CNT",imei
FROM   devices
WHERE  CNT > 1

但是,这会导致错误消息ORA-00904：“CNT”：标识符无效.出于某种原因,将查询包装在另一个查询中会产生所需的结果：

SELECT *
FROM   (SELECT COUNT(*) AS "CNT",imei
        FROM   devices
        GROUP  BY imei)
WHERE  CNT > 1

为什么Oracle在第二个查询中无法识别别名“CNT”？