I'm fishing for a comprehensive and canonical answer for the typical "mysql group by?" question.

Here is some sample data:

   TABLE A
+------+------+----------+-----+
|  id  | foo  | bar      | baz |
+------+------+----------+-----+
|   1  | 1    | hello    | 42  |
|   2  | 0    | apple    | 96  |
|   3  | 20   | boot     | 11  |
|   4  | 31   | unicorn  | 99  |
|   5  | 19   | pumpkin  | 11  |
|   6  | 88   | orange   | 13  |
+------+------+----------+-----+

   TABLE B
+------+------+
| id   | moo  |
+------+------+
|    1 |    1 |
|    2 |   99 |
|    3 |   11 |
+------+------+

Demonstrate and explain the correct use of the GROUP BY clause in MySQL. Touch upon the following points:

• The use of MIN, MAX, SUM, AVG
• The use of HAVING
• Grouping by date, and ranges of dates
• Grouping with an ORDER BY
• Grouping with a JOIN
• Grouping on multiple columns

Bonus points for references to other great answers, the MySQL online manual, and online tutorials on GROUP BY.