How to extract a substring from a delimited string using the SUBSTRING_INDEX() functions?

SUBSTRING_INDEX(str, delim, N) is a MySQL built-in function that returns a substring from a string ending before the Nth delimiter. For example:

SET @str = 'dba.FYIcenter.com';

SELECT SUBSTRING_INDEX(@str, '.', -2);
  -- +--------------------------------+
  -- | SUBSTRING_INDEX(@str, '.', -2) |
  -- +--------------------------------+
  -- | FYIcenter.com                  |
  -- +--------------------------------+

Reference information of the SUBSTRING_INDEX() function:

SUBSTRING_INDEX(str, delim, N): substr
  Returns the substring from string str before N occurrences of the
  delimiter delim. If N is positive, everything to the left of the
  final delimiter (counting from the left) is returned. If N is
  negative, everything to the right of the final delimiter (counting from
  the right) is returned.

Arguments, return value and availability:
  str: Required. The string that will be extracted from.
  delim: Required. The delimiter used in the string.
  N: Required. The number of times to search for the delimiter.
  substr: Return value. The substring extracted.
  Available since MySQL 4.0.

⇒ TO_BASE64() - Base64 Encoding

⇐ SUBSTRING() - Substring at Given Position

⇑ MySQL Functions on Character String Values

⇑⇑ MySQL Function References