确定行是否存在的最佳方法 [英] Best method for determining if a row exists

问题描述

我使用SQL Server和WebMatrix Razor语法来尝试确定用户名是否包含在名为Users的表中。

I am using SQL Server and WebMatrix Razor syntax to try and determine is a username is contained within a table called Users.

我希望的逻辑是：

 bool usernameExists = db.QueryValue("SELECT Username from Users where Username = ?", username);
 if(usernameExists.IsEmpty()){ //username is not in table
    Response.Redirect("Register.cshtml");
 }

进行此操作的最佳做​​法是什么？

What is the best practice for going about this?

推荐答案

最简单的可能是：

bool usernameExists = db.QueryValue("SELECT usernameExists = CASE WHEN EXISTS 
 (SELECT 1 FROM Users WHERE Username = ?) THEN 1 ELSE 0 END", username);

if (!usernameExists) { Response.Redirect("Register.cshtml"); }

虽然我严格地说从SQL Server端。我不知道这是否是从C＃侧的最好的方法。

Though I'm speaking strictly from the SQL Server side. I don't know if this is the best approach from the C# side.

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