Google bigquery 修剪/截断bigquery中数据值的最小字母

目前这是我在google BigQuery中的代码

SELECT *
FROM
(
    SELECT
        CAST(Serial AS integer) AS Serial,
        Latest_Use,
        Total_Hours,
        Devices_Connected
    FROM [dataworks-356fa:FirebaseArchive.PT_Results]
) AS Model_Results
JOIN
(
    SELECT
       CAST(Serial_Number AS integer) AS Serial_Number,
       Status,
       Model_Number
    FROM [dataworks-356fa:FirebaseArchive.Master_List_PT]
) AS Master_List
    ON Model_Results.Serial = Master_List.Serial_Number

但是，我没有得到所有的值，因为一些“序列号”值以“A”或“B”结尾，而“序列号”值则没有。我该怎么做，要么在5个字符后修剪每个序列的值#，要么截断值以去掉最后一个字符

这有用吗

SELECT *
FROM
(
    SELECT
        CAST(Serial AS integer) AS Serial,
        Latest_Use,
        Total_Hours,
        Devices_Connected
    FROM [dataworks-356fa:FirebaseArchive.PT_Results]
) AS Model_Results
JOIN
(
    SELECT
       CAST(Serial_Number AS integer) AS Serial_Number,
       Status,
       Model_Number
    FROM [dataworks-356fa:FirebaseArchive.Master_List_PT]
) AS Master_List
    ON Model_Results.Serial = REGEXP_EXTRACT(Master_List.Serial_Number, r'\d+')