EF Code First: How to get random rows

Question

How can I build a query where I would retrieve random rows?

If I were to write it in SQL then I would put an order by on newid() and chop off n number of rows from the top. Anyway to do this in EF code first?

I have tried creating a query that uses newid() and executing it using DbSet.SqlQuery(). while it works, its not the cleanest of solutions.

Also, tried retrieve all the rows and sorting them by a new guid. Although the number of rows are fairly small, its still not a good solution.

Any ideas?

Answer 1

Just call:

something.OrderBy(r => Guid.NewGuid()).Take(5) 

Answer 2

Comparing two options:

---

Skip(random number of rows)

Method

private T getRandomEntity<T>(IGenericRepository<T> repo) where T : EntityWithPk<Guid> {     var skip = (int)(rand.NextDouble() * repo.Items.Count());     return repo.Items.OrderBy(o => o.ID).Skip(skip).Take(1).First(); } 

• Takes 2 queries

Generated SQL

SELECT [GroupBy1].[A1] AS [C1] FROM   (SELECT COUNT(1) AS [A1]         FROM   [dbo].[People] AS [Extent1]) AS [GroupBy1];  SELECT TOP (1) [Extent1].[ID]            AS [ID],                [Extent1].[Name]          AS [Name],                [Extent1].[Age]           AS [Age],                [Extent1].[FavoriteColor] AS [FavoriteColor] FROM   (SELECT [Extent1].[ID]                                  AS [ID],                [Extent1].[Name]                                AS [Name],                [Extent1].[Age]                                 AS [Age],                [Extent1].[FavoriteColor]                       AS [FavoriteColor],                row_number() OVER (ORDER BY [Extent1].[ID] ASC) AS [row_number]         FROM   [dbo].[People] AS [Extent1]) AS [Extent1] WHERE  [Extent1].[row_number] > 15 ORDER  BY [Extent1].[ID] ASC; 

---

Guid

Method

private T getRandomEntityInPlace<T>(IGenericRepository<T> repo) {     return repo.Items.OrderBy(o => Guid.NewGuid()).First(); } 

Generated SQL

SELECT TOP (1) [Project1].[ID]            AS [ID],                [Project1].[Name]          AS [Name],                [Project1].[Age]           AS [Age],                [Project1].[FavoriteColor] AS [FavoriteColor] FROM   (SELECT NEWID()                   AS [C1],                [Extent1].[ID]            AS [ID],                [Extent1].[Name]          AS [Name],                [Extent1].[Age]           AS [Age],                [Extent1].[FavoriteColor] AS [FavoriteColor]         FROM   [dbo].[People] AS [Extent1]) AS [Project1] ORDER  BY [Project1].[C1] ASC