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Unloading Data from Databend

Databend provides a variety of tools for loading and unloading data. One of the methods of unloading data from Databend is using the COPY INTO <location> command.

This command is used to export data from a Databend table or query into a file format such as CSV, Parquet, Or JSON.

Unloading Data​

Creating a Stage​

Before unloading data, you need to create a stage, which acts as a storage location for the exported data. You can choose to create an external or internal stage, depending on your requirements.

Here's an example of how to create an external stage:

CREATE STAGE unload url='s3://unload/files/' connection=(aws_key_id='1a2b3c' aws_secret_key='4x5y6z');

Unloading Data​

Once you have created a stage, you can use the COPY INTO command to export data:

COPY INTO @unload FROM (SELECT * FROM numbers(10000000)) FILE_FORMAT = (TYPE = PARQUET);

Verifying the Exported Data​

You can use the LIST STAGE command to show the exported data files:

LIST @unload;
+--------------------------------------------------------+----------+------------------------------------+-------------------------------+---------+
| name                                                   | size     | md5                                | last_modified                 | creator |
+--------------------------------------------------------+----------+------------------------------------+-------------------------------+---------+
| data_8799a438-9788-4dcb-bd45-3aa23ea9c6a3_32_0.parquet | 41486538 | "F187251F37666928684DBED4AF0523DF" | 2023-02-12 03:45:03.000 +0000 | NULL    |
+--------------------------------------------------------+----------+------------------------------------+-------------------------------+---------+

You can also query the exported data to confirm its validity:

SELECT sum(number) FROM @unload (PATTERN => '.*parquet');
+----------------+
| sum(number)    |
+----------------+
| 49999995000000 |
+----------------+