what is the difference between %s and %S in mysql

Question

I was answering a question about SQL formatting recently and noticed in documentation two ways to define seconds %s and %S

They both seem to do described the same:
%S - Seconds (00..59)
%s - Seconds (00..59)

and

SELECT STR_TO_DATE('2014-07-09 23:30:00', '%Y-%m-%d %H:%i:%s');
SELECT STR_TO_DATE('2014-07-09 23:30:00', '%Y-%m-%d %H:%i:%S');

give same result.

So is it historic like leftovers from some early version or they are two different things in some way?

Answer 1

They are the same things. I think its the historic leftover. As they both produce the same result.

I think the layout given by Mark in the same link is helpful:

+--------------+----------+--------------------+
| metric       | variant  | result             |
+--------------+----------+--------------------+
| microseconds | %f       | 000000..999999     |
| seconds      | %s or %S | 00..59             |
| minutes      | %i       | 00..59             |
| hours        | %H       | 00...23            |
|              | %h or %I | 00...12            |
|              | %k       | 0...23             |
|              | %l       | 1...12             |
| day          | %a       | Sun...Sat          |
|              | %D       | 1st, 2nd, 3rd      |
|              | %d       | 0.31               |
|              | %e       | 0..31              |
|              | %j       | 001...366          |
|              | %W       | Sunday...Sat       |
|              | %w       | 0...6              |
| week         | %U       | 00...53 per Sun    |
|              | %u       | 00...53 per Mon    |
| *            | %V       | 01...53 per Sun    |
| *            | %v       | 01...53 per Mon    |
| month        | %b       | Jan...Dec          |
|              | %c       | 0...12             |
|              | %M       | January...December |
|              | %m       | 00...12            |
| year         | %Y       | 1999               |
|              | %y       | 99                 |
| *            | %X       | 1999               |
| *            | %x       | 99                 |
| time         | %r       | 01:31:12 pm        |
|              |          | %T | 01:31:12 pm   |
|              | %p       | AM or PM           |
| Percent sign | %%       | %                  |
+--------------+----------+--------------------+