Google bigquery BigQuery:即使在应用别名之后，列名也不明确

亲爱的社区：

我试图运行一个查询，使用别名在一个键上连接两个数据集，但验证器显示一个错误查询错误：列名visit\u id不明确

SELECT visit_id as a
FROM `dashboards.test.visits` FULL JOIN `dashboards.test.tracks` on visit_id;

**Schema for `dashboards.test.visits`**

Field name  Type    Mode    
visit_time  TIMESTAMP   NULLABLE    
visit_id    INTEGER NULLABLE    
device_id   INTEGER NULLABLE    
traffic_source  STRING  NULLABLE    
pages_viewed    FLOAT   NULLABLE    

**Schema `dashboards.test.tracks`**

Field name  Type    Mode    
track_time  TIMESTAMP   NULLABLE    
track_id    FLOAT   NULLABLE    
visit_id    FLOAT   NULLABLE    

---

模棱两可的是专栏的来源，因为它可以来自访问和跟踪。请尝试以下操作：

SELECT a.visit_id
FROM `dashboards.test.visits` a
FULL JOIN `dashboards.test.tracks` b
on a.visit_id = b.visit_id;

---

模棱两可的是专栏的来源，因为它可以来自访问和跟踪。请尝试以下操作：

SELECT a.visit_id
FROM `dashboards.test.visits` a
FULL JOIN `dashboards.test.tracks` b
on a.visit_id = b.visit_id;

---

可以使用来避免此错误

SELECT visit_id
FROM `dashboards.test.visits` 
FULL JOIN `dashboards.test.tracks` 
USING(visit_id);

---

可以使用来避免此错误

SELECT visit_id
FROM `dashboards.test.visits` 
FULL JOIN `dashboards.test.tracks` 
USING(visit_id);