Resolving the SQL compilation error in Snowflake when copying JSON from S3

Discover how to fix the `SQL compilation error` related to JSON data types in Snowflake. Learn about the proper column types to use for successful data loading.
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Resolving the SQL compilation error in Snowflake when copying JSON from S3

If you're working with Snowflake and trying to copy JSON data from Amazon S3, you may run into an annoying issue that states:

SQL compilation error: JSON file format can produce one and only one column of type variant or object or array when copying from S3 to Snowflake.

This error can be confusing, especially if you're not familiar with the requirements of JSON format handling in Snowflake tables. In this post, we'll break down the problem and provide a simple solution to ensure a smooth data transfer from S3 to Snowflake.

Understanding the Problem

The root of the issue lies in how Snowflake handles JSON data types. When you try to load JSON data, Snowflake expects a specific data type based on your table's schema. In your attempt to load a JSON object into a table with a VARCHAR column, Snowflake throws an error because JSON data must be stored in a compatible format.

Your Current Setup

JSON File in S3: You have a JSON file structured like this:

[[See Video to Reveal this Text or Code Snippet]]

Table in Snowflake: You created a table named test_firehose with a VARCHAR column called data.

Copy Statement: Your SQL command was:

[[See Video to Reveal this Text or Code Snippet]]

Upon executing this, you encountered the compilation error.

Solution: Change Column Data Type to VARIANT

To resolve the issue, you need to adjust the column data type in your Snowflake table to appropriately handle JSON data. Here’s how you can do it:

Modify the Table Structure: Instead of using a VARCHAR column, use a VARIANT data type, which is designed to handle semi-structured data like JSON efficiently. Update your table structure by running:

[[See Video to Reveal this Text or Code Snippet]]

Re-run the COPY Command: Once you have changed the column type to VARIANT, execute the COPY command again:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Now, by using a VARIANT data type for your JSON column, you will be able to successfully copy the content from your S3 bucket into Snowflake without encountering SQL compilation errors. This change ensures that you're adhering to Snowflake's requirements for handling JSON data format effectively.

By understanding and adjusting the table schema accordingly, you can manage JSON data more seamlessly in your data workflows. Happy querying!