How to select random row from each group in MySQL?

Question

How to randomly get one row from each group in MySQL? for ex:

A 145 <br/>
A 589***********GROUP 1 <br/>
A 576 <br/>

B 246************GROUP 2 <br/>
B 456 <br/>

C 558 <br/>
C 478***********GROUP 3 <br/>
C 4756 <br/>

want to get any row from each group.Thanks in advance :)

Answer 1

ORDER BY rand() calculates a random value at every read for every row. It is better to calculate a random sortorder once a day (or once an hour) for every row and store it in the detailed table, and for selecting the value just produce a temp-table with a compare-randomvalue for every category.

I just posted a solution in Combining queries for speed .