How to Efficiently Retrieve a Random Row with Conditions Using Linq to SQL?

LINQ to SQL conditions High -efficiency random retrieval data line

The use of Linq to SQL to query the database is a powerful way to retrieve relational database data. However, when applying specific conditions, you can bring some challenges when you choose a random line. This article discusses a solution to this problem efficiently.

Using analog user custom function (UDF)

Linq to SQL has no direct way to choose random line. To overcome this limit, a simulation UDF can be created in the database. This can be achieved by adding a method to some data contexts, as shown below:

This UDF acts as a placement to enable random sorting in SQL Server.

partial class MyDataContext {
     [Function(Name="NEWID", IsComposable=true)] 
     public Guid Random() 
     { // 证明我们的C#代码未使用... 
         throw new NotImplementedException(); 
     }
}

<随> Apply random sorting

Once the simulation UDF is in place, you can sort the Linq query by calling the method. This will indicate that the database uses the <> function to perform random sorting.

This query will retrieve a single random line that meets the specified conditions. ctx.Random() NEWID() <能> Performance precautions

var cust = (from row in ctx.Customers
           where row.IsActive // 你的筛选条件
           orderby ctx.Random()
           select row).FirstOrDefault();

It should be noted that using this UDF method may affect the performance of large tables. In this case, a more effective method is to determine the number of lines (using the

method), generate a random index, and then use the

and methods to search random lines.

The counting method

Count() Skip()

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