How to decode a Base64 string using the FROM_BASE64() function?

FROM_BASE64(str) is a MySQL built-in function that decodes a Base64 string. For example:

SELECT FROM_BASE64('RllJ'), TO_BASE64('FYI');
  -- +---------------------+------------------+
  -- | FROM_BASE64('RllJ') | TO_BASE64('FYI') |
  -- +---------------------+------------------+
  -- | FYI                 | RllJ             |
  -- +---------------------+------------------+

SELECT FROM_BASE64('My4xNA=='), TO_BASE64(3.14);
  -- +-------------------------+-----------------+
  -- | FROM_BASE64('My4xNA==') | TO_BASE64(3.14) |
  -- +-------------------------+-----------------+
  -- | 3.14                    | My4xNA==        |
  -- +-------------------------+-----------------+

Reference information of the FROM_BASE64() function:

FROM_BASE64(str): bin
  Takes a string encoded with the base-64 encoded rules used by
  TO_BASE64() and returns the decoded result as a binary string.

Arguments, return value and availability:
  str: Required. The input Base64 string.
  bin: Return value. The decoded bytes.
  Available since MySQL 5.7.

Related MySQL functions:

• TO_BASE64() - Base64 Encoding

⇒ HEX() - Calculate HEX representation

⇐ FIND_IN_SET() - Find Substring in List String

⇑ MySQL Functions on Character String Values

⇑⇑ MySQL Function References