如何从一个PostgreSQL表中检索数据的随机行？ [英] How to retrieve randomized data rows from a postgreSQL table?

问题描述

我有一个PostgreSQL服务器数据库表上几乎 3000000 行，我需要的所有行保存到一个CSV文件。这里的问题是，该行必须被保存在一个不同的随机我每次运行过程时间顺序。

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.

值得一提的是，这是一个C＃ 。WinForms应用程序

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

我试图将数据加载到一个List<>以及使用的洗牌算法，但它采取了永远结束了，我真的需要它要快。我想直接做在查询会快很多，但我并没有对如何做到这一点的线索。

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.

推荐答案

通常情况下，你可以只 ORDER BY 你的数据库味道随机函数，如

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

SELECT * FROM table ORDER BY RANDOM()

这可能是因为洗牌慢列表中，这取决于该数据库服务器或产品上。

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

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