如何在 Azure Synapse 无服务器 SQL 池中使用 CETAS 创建外部表时添加自动递增列？

Question

In server-less SQL Pool, Identities are not supported, is there any better way to add an auto-incremented column while creating an external table using Select Statement.

    CREATE EXTERNAL TABLE temp.example_table
    WITH 
    (
        DATA_SOURCE = data_source_name,
        LOCATION = 'TempTables/exanple_table',
        FILE_FORMAT = parquet_file_format
    )
    AS 


    SELECT  name                                    AS user_name
         , code                                        AS user_code
      FROM schema.example_table
 

How can we add an auto-increment column along with the name and code column in external table?

I want something like -

id	user_name	user_code
1	Indrajeet	SinghI
2	Himanshu	RawatH
3	Akshay	SharmaA

Answer 1

Try ROW_NUMBER:

    CREATE EXTERNAL TABLE temp.example_table
    WITH 
    (
        DATA_SOURCE = data_source_name,
        LOCATION = 'TempTables/exanple_table',
        FILE_FORMAT = parquet_file_format
    )
    AS 


    SELECT  ROW_NUMBER() OVER (ORDER BY code) as id
         , name                                    AS user_name
         , code                                        AS user_code
      FROM schema.example_table

One warning. If you run the same tomorrow it won't necessarily be the same id for Akshay. So this may not be appropriate except for a one-time load.

If stability cross days is important you might try HASHBYTES('MD5', code) as id . On a small table that should be unique. But on a large table you may have hash collisions and it not be unique.