Question

我有在c＃中运行的代码，这段代码的作用是什么：

循环访问用户列表并更新表中的行。

UPDATE CustomerUser 
                SET
                    LoginName = @LoginName,
                    UserName = @UserName,    
                    IsActive = @IsActive, 
                    IsDeleted = @IsDeleted,
                    DeletedDate = @DeletedDate,
                    Modified = CURRENT_TIMESTAMP()
                WHERE ID = @CustomerUserID;

在c＃代码中，然后对LoginName和userName列进行一些连接。

我想用一个SQL语句替换那个缓慢的C＃进程，该语句执行类似我下面的操作。我对SQL有足够的了解，认为我的问题可能完全是疯了，但在你问之前永远不会知道。

UPDATE CustomerUser 
                    SET
                        LoginName = select concat( login,uniqueid) from CustomerUser where id **this would be an ID that is in the IN() of parent query**
                        UserName = @UserName,    
                        IsActive = @IsActive, 
                        IsDeleted = @IsDeleted,
                        DeletedDate = @DeletedDate,
                        Modified = CURRENT_TIMESTAMP()
                    WHERE ID **IN(1,2,3,4, etc...)**;

Answer 1

您可以更改查询以删除SELECT子查询，只需执行以下操作：

UPDATE CustomerUser
SET LoginName = CONCAT(LoginName, UserName)
-- Other fields, etc..
WHERE ID **IN(1,2,3,4, etc...)**;

如果您在C＃中这样做，我建议使用Entity Framework而不是SQL Query字符串。我只将它与SQL Server一起使用，但是这里讨论了与MySQL一起使用的信息：

Using MySQL with Entity Framework

使用Entity，您可以通过编写一个包含所有id列表的函数来更新为parmeter：

void UpdateCustomerUsers(ICollection<int> ids)
{
using (var context = new MyDbContext())
{
    var customerUsers = context.CustomerUsers.Where(cu => ids.Contains(cu.ID));

    foreach (var cu in customerUsers)
    {
        cu.LoginName = cu.LoginName + cu.UserName;
        cu.Modified = DateTime.Now;
        // and so on...
    }

    context.SaveChanges();
}
}

Answer 2

您可以将更新与加入

一起使用

  UPDATE CustomerUser   as t1
  INNER JOIN  (  
           id from CustomerUser WHERE ID IN(1,2,3,4, etc...)
  ) t2  on t1.ID=t2.id
  SET
      LoginName = select concat( t1.login, t1.uniqueid) 
      UserName = @UserName,    
      IsActive = @IsActive, 
      IsDeleted = @IsDeleted,
      DeletedDate = @DeletedDate,
      Modified = CURRENT_TIMESTAMP()

使用自定义值更新

2 个答案: