Export query results to Blob Storage

This document describes how to export the result of a query that runs against a BigLake table to your Azure Blob Storage.

For information about how data flows between BigQuery and Azure Blob Storage, see Data flow when exporting data.

Limitations

For a full list of limitations that apply to BigLake tables based on Amazon S3 and Blob Storage, see Limitations.

Before you begin

Ensure that you have the following resources:

A connection to access your Blob Storage. Within the connection, you must create a policy for the Blob Storage container path that you want to export to. Then, within that policy, create a role that has the Microsoft.Storage/storageAccounts/blobServices/containers/write permission.
An Blob Storage BigLake table.

If you are on the capacity-based pricing model, then ensure that you have enabled the BigQuery Reservation API for your project. For information about pricing, see BigQuery Omni pricing.

Export query results

BigQuery Omni writes to the specified Blob Storage location regardless of any existing content. The export query can overwrite existing data or mix the query result with existing data. We recommend that you export the query result to an empty Blob Storage container.

In the Google Cloud console, go to the BigQuery page.

Go to BigQuery
In the Query editor field, enter a GoogleSQL export query:
```
EXPORT DATA WITH CONNECTION \`CONNECTION_REGION.CONNECTION_NAME\`
OPTIONS(
  uri="azure://AZURE_STORAGE_ACCOUNT_NAME.blob.core.windows.net/CONTAINER_NAME/FILE_PATH/*",
  format="FORMAT"
)
AS QUERY
```
Replace the following:
- CONNECTION_REGION: the region where the connection was created.
- CONNECTION_NAME: the connection name that you created with the necessary permission to write to the container.
- AZURE_STORAGE_ACCOUNT_NAME: the name of the Blob Storage account to which you want to write the query result.
- CONTAINER_NAME: the name of the container to which you want to write the query result.
- FILE_PATH: the path where you want to write the exported file to. It must contain exactly one wildcard * anywhere in the leaf directory of the path string, for example, ../aa/*, ../aa/b*c, ../aa/*bc, and ../aa/bc*. BigQuery replaces * with 0000..N depending on the number of files exported. BigQuery determines the file count and sizes. If BigQuery decides to export two files, then * in the first file's filename is replaced by 000000000000, and * in the second file's filename is replaced by 000000000001.
- FORMAT: supported formats are JSON, AVRO, CSV, and PARQUET.
- QUERY: the query to analyze the data that is stored in a BigLake table.

Troubleshooting

If you get an error related to quota failure, then check if you have reserved capacity for your queries. For more information about slot reservations, see Before you begin in this document.

What's next

Learn about BigQuery Omni.
Learn how to export table data.
Learn how to query data stored in Blob Storage.
Learn how to set up VPC Service Controls for BigQuery Omni.