MySQL select 10 random rows from 600K rows fast

Question

How can I best write a query that selects 10 rows randomly from a total of 600k?

Answer 1

This is super fast and is 100% random even if you have gaps.

1. Count the number x of rows that you have available SELECT COUNT(*) as rows FROM TABLE
2. Pick 10 distinct random numbers a_1,a_2,...,a_10 between 0 and x
3. Query your rows like this: SELECT * FROM TABLE LIMIT 1 offset a_i for i=1,...,10

I found this hack in the book SQL Antipatterns from Bill Karwin.