Loading dynamic files

Question

Hello, We are trying to load data from an output file to a delta table in azure but there will be some additional columns added everytime the output file is created. What is the best possible solution to load the output file to a delta table in case the file has additional columns in it.. @aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

Answer 1

Hi Niren Adhikary,

Thank you for posting query in Microsoft Q&A Platform.

If you are loading data from an output file to a delta table in Azure and the output file has additional columns added to it each time it is created, you can use the following approach to handle the additional columns:

Create the delta table with a schema that includes all the columns that are present in the output file. You can use the CREATE TABLE statement to create the delta table with the required schema.

When you load the data from the output file to the delta table, use the MERGE INTO statement to merge the data from the output file with the data in the delta table. The MERGE INTO statement allows you to insert new rows, update existing rows, or delete rows based on a condition.

In the MERGE INTO statement, use the WHEN NOT MATCHED BY TARGET clause to insert new rows into the delta table. This clause allows you to specify the columns that are present in the output file but not in the delta table. You can use the NULL value to insert default values for these columns.

In the MERGE INTO statement, use the WHEN MATCHED clause to update existing rows in the delta table. This clause allows you to specify the columns that are present in the output file but not in the delta table. You can use the SET clause to update the values of these columns.

Here is an example of how you can use the MERGE INTO statement to load data from an output file to a delta table:

MERGE INTO delta_table AS target
USING output_file AS source
ON target.id = source.id
WHEN MATCHED THEN
  UPDATE SET target.column1 = source.column1, target.column2 = source.column2, ...
WHEN NOT MATCHED BY TARGET THEN
  INSERT (id, column1, column2, ...) VALUES (source.id, source.column1, source.column2, ...)

In this example, delta_table is the name of the delta table, output_file is the name of the output file, and id, column1, column2, etc. are the names of the columns in the delta table and the output file. The MERGE INTO statement merges the data from the output file with the data in the delta.

Hope this helps. Please let me know if any further queries.

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