BQ添加格式Table.column时无法识别列名

Question

情况：我有两个具有相同列名的表，称为“忠诚度编号”，我想使用此列作为主键来左连接两个表。

尝试按如下方式为列名称添加别名不起作用，因为 BQ 会将“customer_flight_data.Loyalty_Number”插入到列中，而不是实际数字。

SELECT `customer_flight_data.Loyalty_Number` AS loyalty_number1,

FROM `case-study-airline-69374.customer_flight_activity.customer_flight_data`

输出： 列忠诚度_number1

1. customer_flight_data.Loyalty_Number
   

我尝试从 table.column 中删除“`”，但随后我收到了

错误：无法识别的名称：customer_flight_data。

现在唯一有效的是：

SELECT Loyalty_Number FROM `case-study-airline-69374.customer_flight_activity.customer_flight_data` 

Answer 1

正如 nbk 建议的那样，您可以使用表的别名来标识列，也可以使用每列的完整表标识符，而不将该列包含到 qoutes 中。

--Complete Table identifier
SELECT `case-study-airline-69374.customer_flight_activity.customer_flight_data`.Loyalty_Number AS loyalty_number1,
FROM `case-study-airline-69374.customer_flight_activity.customer_flight_data`

--Alias
SELECT tablealias.Loyalty_Number AS loyalty_number1,
FROM `case-study-airline-69374.customer_flight_activity.customer_flight_data` as tablealias

--Example for the left join
SELECT 
  leftsidetable.Loyalty_Number AS loyalty_number1,
  rightsidetable.Loyalty_Number AS loyalty_number2
FROM `case-study-airline-69374.customer_flight_activity.customer_flight_data` as leftsidetable
LEFT JOIN `case-study-airline-69374.customer_flight_activity.customer_flight_data` as rightsidetable ON leftsidetable.loyalty_number = rightsidetable.loyalty_number