Decoding base64 in AWS Athena requires two steps. First, we have to use the from_base64 function to get a binary representation of the decoded content. We don’t get text automatically because we can use base64 to encode as a string any binary data, for example, a picture.

Therefore, Athena does not know that the content is a string. Because of that, we have to use the from_utf8 function to convert the binary data into text.

The complete SQL looks like this:

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select from_utf8( from_base64(base64_encoded_column) ) FROM some_table

One more thing. Never, ever say that base64 is encryption. It is not. That is just a method of representing binary data as a string, so you can send it to/from a REST API as a JSON object or include it in an URL.