Question

I have a table on a PostgreSQL server database with almost 3 million rows and I need to save all rows to a CSV file. The problem here is that the rows must be saved in a different random order each time I run the process.

Worth noting that it’s a C# WinForms app.

I tried loading the data into a List<> and using a shuffling algorithm but it took forever to finish, and I realy need it to be fast. I think doing it directly in the query will be much faster but I don’t have a clue on how to do it.

Answer 1

Typically, you can just ORDER BY a random function of your database flavor, like

SELECT * FROM table ORDER BY RANDOM()

This might be as slow as shuffling the list, depending on the database server or product.