SQL语法错误，为“0”；加上；条款

在WHERE子句中使用WITH alias时遇到奇怪的问题。 问题SQL语句：

WITH CROOM AS (SELECT id FROM classroom WHERE floor = 1)
SELECT DISTINCT teacher_id
FROM timetable
WHERE classroom_id IN CROOM;

错误是ORA-00904：“CROOM”：无效标识符

虽然这两个语义相似的语句都非常有效

SELECT DISTINCT teacher_id
FROM timetable
WHERE classroom_id IN (SELECT id FROM classroom WHERE floor = 1);

WITH CROOM AS (SELECT id FROM classroom WHERE floor = 1)
SELECT DISTINCT T.teacher_id 
FROM timetable T JOIN CROOM ON (T.classroom_id = CROOM.id);

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为什么它不能识别WHERE中的别名，而在FROM子句中接受它呢？

您应该使用CROOM作为表。例如，您可以编写：

WITH CROOM AS (SELECT id FROM classroom WHERE floor = 1)
SELECT DISTINCT teacher_id
FROM timetable
WHERE classroom_id IN (select id from CROOM);