Random Sampling in Google BigQuery

Question

I just discovered that the RAND() function, while undocumented, works in BigQuery. I was able to generate a (seemingly) random sample of 10 words from the Shakespeare datase

Answer 1

Great to know RAND() is available!

In my case I needed a predefined sample size. Instead of needing to know the total number of rows and do the division sample size over total rows, I'm using the following query:

SELECT word, rand(5) as rand
FROM [publicdata:samples.shakespeare]
order by rand
#Sample size needed = 10
limit 10

Summarizing, I use ORDER BY + LIMIT to ramdomize and then extract a defined number of samples.