How to obtain the n-th value of a field expression in the current result set window using the NTH_VALUE() function?

NTH_VALUE(exp, n) is a MySQL built-in window function that returns the n-th value of a field expression in the current result set window. For example:

SELECT help_topic_id AS tip, help_category_id AS cid,
  name, NTH_VALUE(name, 2) OVER w
  FROM mysql.help_topic
  WINDOW w AS (PARTITION BY help_category_id);
  -- +-----+-----+----------------+---------------------------+
  -- | tip | cid | name           | NTH_VALUE(name, 2) OVER w |
  -- +-----+-----+----------------+---------------------------+
  -- |   0 |   1 | HELP_DATE      | HELP_VERSION              |
  -- |   1 |   1 | HELP_VERSION   | HELP_VERSION              |
  -- |   2 |   2 | AUTO_INCREMENT | BIT                       |
  -- |   6 |   2 | BIT            | BIT                       |
  -- |   7 |   2 | TINYINT        | BIT                       |
  -- |   8 |   2 | BOOLEAN        | BIT                       |
  -- |   9 |   2 | SMALLINT       | BIT                       |
  -- ...
  -- +-----+-----+----------------+---------------------------+

Reference information of the NTH_VALUE() function:

NTH_VALUE(exp, n): val
  Returns the n-th value of a field expression
  in the current result set window.

Arguments, return value and availability:
  exp: Required. The field expression to be evaluated.
  n: Required. The position of row in the current window.
  val: Return value. The n-th value of exp in the current window.
  Available since MySQL 8.

Related MySQL functions:

• FIRST_VALUE() - First Value of Result Set Window
• LAST_VALUE() - Last Value of Result Set Window
• NTH_VALUE() - N-th Value of Result Set Window

⇒ NTILE() - Dividing Window into N Tiles

⇐ LEAD() - N-Row after Current Row within Window

⇑ MySQL Functions on Result Set Windows

⇑⇑ MySQL Function References