使用实体框架获取多条随机记录？

Question

I have checked this answered question and other articles on Stack Overflow. I prefer the Skip method. However, they are all for single record. Now assume I want to take 20 random records from a table, how can I do that?

I am trying two possibilities:

1. Generate an array of indexes and use Skip for each. This, however, results in 20 queries (and each is ordered by Id too).

2. Fetch the list of all Ids and pick randomly into an array and perform a 2nd query for detailed info all selected Ids.

3. Or just use OrderBy as the other post suggested. I think this can be bad because the entire table is ordered?

Please tell me if there is any better solution.

Answer 1

Can you not use a Stored Proc to do this for you?

So your StoredProcs job is to return 20 records to the caller (I guess this is some Online Exam :D)

on the sql side you can use SQL Rand() to generate random numbers for all rows in your Table. Then Order them by Asc/Desc values of this Random column and Pick top 20.

Answer 2

Ordering the table by randomized guid will not leave any effects on the table. The Linq solution achieves what you want to do.

private IEnumerable<MyClass> GetRandomItems(int n)
{
    return _dbContext.MyClass.OrderBy(x => Guid.NewGuid()).Take(n);
}