检查数据库中是否已存在电子邮件

Question

我想检查电子邮件地址是否已经存在于数据库中，首先，我想提一下，来自互联网的NO代码不起作用。所以请快速帮助和理解编程问题，我很绿。以下是有关通话的基本信息等。

string constring = "datasource=localhost;port=3306;username=admin;password=admin"; 

string query = "select * from test.user where email='" + emailtextbox.Text + "';"; 

MySqlConnection conDatabase = new MySqlConnection(constring); 
MySqlCommand cmddatabase = new MySqlCommand(query, conDatabase); 

电子邮件被称为“电子邮件”的列。

Answer 1

试试这个代码

string query = "select * from test.user where replace(email,' ','')='" 
+ emailtextbox.Text.Trim() + "'"; 

MySqlConnection conDatabase = new MySqlConnection(constring); 
MySqlCommand cmddatabase = new MySqlCommand(query, conDatabase); 

Answer 2

解决方案1：您可以TrimEmailID由用户输入然后比较。

试试这个：

string query = "select count(*) from test.user where email = @email"; 

MySqlConnection conDatabase = new MySqlConnection(constring); 

MySqlCommand cmddatabase = new MySqlCommand(query, conDatabase); 
cmddatabase.Parameters.AddWithValue("@email",emailtextbox.Text.Trim()); 

conDatabase.Open(); 
int count = Convert.ToInt32(cmddatabase.ExecuteScalar()); 

if(count > 0) 
{ 
    // yes emailid exists already 
}