如何从 mysql 中读取一行？

Question

我在 mysql 中有用户配置文件，我想读取一行（某些用户的）并将值添加到对象 "user"

这是我的部分代码：（ return 用户的函数）

connection.Open();

person person_1 = new person();

//1. Read name
string sql = "select name from profili where name=@name and surname=@surname";
    cmd = new MySqlCommand(sql, konekcija);
    cmd.Parameters.Add("@name", name);
   cmd.Parameters.Add("@surname", surname);

MySqlDataReader reader = cmd.ExecuteReader();

if (reader.Read()) {

  person_1.name = reader["name"].ToString();


//2. Read surname
string sql = "select surname from profili where name=@name and surname=@surname";
cmd = new MySqlCommand(sql, konekcija);
cmd.Parameters.Add("@name", name);
   cmd.Parameters.Add("@surname", surname);
    person_1.surname = reader["surname"].ToString();
return person_1;

有了这个我只得到名字，姓氏是空的（在调试器中看到）

Answer 1

你的代码毫无意义。您已经知道姓氏和姓名，因为您将它们作为 WHERE 条件的参数传递。其中一部分，姓氏为空的问题是您不执行第二个命令。

您应该添加

//2. Read surname
string sql = "select surname from profili where name=@name and surname=@surname";
cmd = new MySqlCommand(sql, konekcija);
cmd.Parameters.Add("@name", MySqlType.VarChar).Value = name;
cmd.Parameters.Add("@surname", MySqlType.VarChar).Value = surname;
reader = cmd.ExecuteReader();
person_1.surname = reader["surname"].ToString();

也就是说，执行两次命令来检索一行是没有意义的。您的查询文本可以轻松添加您想要检索的所有列名，并且只执行一次读取

//1. Read the row matching the known surname and name 
string sql = @"select name, surname, column1, column2, colx 
              from profili where name=@name and surname=@surname";

cmd = new MySqlCommand(sql, konekcija);
cmd.Parameters.Add("@name", MySqlType.VarChar).Value = name;
cmd.Parameters.Add("@surname", MySqlType.VarChar).Value = surname;
MySqlDataReader reader = cmd.ExecuteReader();
if (reader.Read()) {
   person_1.name = reader["name"].ToString();
   person_1.surname = reader["surname"].ToString();
   person_1.Property1 = reader["column1"].ToString();
   ...and so on for other columns

如何从 mysql 中读取一行？

How to read one row from mysql?

c#

mysql

row