在插入sql数据库之前检查现有记录

我创建了一个简单的asp.net表单，它允许用户查看培训的日期列表并注册该日期，他们手动输入他们的名称和employeeid（我不想让dulpicate雇工IDS），所以我需要弄清楚如何检查在C＃..在插入sql数据库之前检查现有记录

代码：

public string GetConnectionString() 
    { 
     //sets the connection string from your web config file "ConnString" is the name of your Connection String 
     return System.Configuration.ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString; 


    } 

    private void checkContraint() 
    { 

     SqlConnection conn = new SqlConnection(GetConnectionString()); 
     string sql = "Select "; //NEED HELP HERE 

    } 


    private void InsertInfo() 
    { 
     var dateSelected = dpDate.SelectedItem.Value; 
     SqlConnection conn = new SqlConnection(GetConnectionString()); 

     string sql = "INSERT INTO personTraining (name,department,title,employeeid,training_id, training,trainingDate,trainingHour, trainingSession)SELECT @Val1b+','[email protected],@Val2,@Val3,@Val4,training_id,training,trainingDate,trainingHour,trainingSession FROM tbl_training WHERE training_id [email protected]_id "; 


     try 
     { 
      conn.Open(); 
      SqlCommand cmd = new SqlCommand(sql, conn); 


      cmd.Parameters.AddWithValue("@Val1", txtName.Text); 
      cmd.Parameters.AddWithValue("@Val1b", txtLname.Text); 
      cmd.Parameters.AddWithValue("@Val2", txtDept.Text); 
      cmd.Parameters.AddWithValue("@Val3", txtTitle.Text); 
      cmd.Parameters.AddWithValue("@Val4", txtEmployeeID.Text); 

      //Parameter to pass for the select statement 
      cmd.Parameters.AddWithValue("@training_id", dateSelected); 
      cmd.CommandType = CommandType.Text; 
      //cmd.ExecuteNonQuery(); 

      int rowsAffected = cmd.ExecuteNonQuery(); 
      if (rowsAffected == 1) 
      { 

       //Success notification   // Sends user to redirect page 

       Response.Redirect(Button1.CommandArgument.ToString()); 
       ClearForm(); 
      } 
      else 
      { 
       //Error notification  

      } 
     } 
     catch (System.Data.SqlClient.SqlException ex) 
     { 
      string msg = "Insert Error:"; 
      msg += ex.Message; 
      throw new Exception(msg); 

     } 
     finally 
     { 
      conn.Close(); 
     } 
    } 

    protected void Button1_Click(object sender, EventArgs e) 
    { 

     checkContraint(); 
     InsertInfo();

来源

2011-11-14 user959443

您是否需要将其限制为每个员工ID的一个培训课程？或者每个日期一个，每个会话一个，等等？ –

只需在整个表格中限制一个员工ID（唯一） – user959443

Royi的答案看起来就是这样。虽然不是检查约束方法的单独验证查询，但它应该在InsertInfo中打到错误通知处理程序。 –

这样，你的查询将数据插入仅如果不是已经存在

string sql = "INSERT INTO personTraining (name,department,title,employeeid,training_id, training,trainingDate,trainingHour, trainingSession)SELECT @Val1b+','[email protected],@Val2,@Val3,@Val4,training_id,training,trainingDate,trainingHour,trainingSession FROM tbl_training WHERE training_id [email protected]_id and not exists (select 1 from personTraining pp where pp [email protected]) ";

来源

2011-11-14 21:22:51

我从来没有见过从personTraining pp选择1，其中pp .employeeid = @ Val4 ....它有什么作用？ – user959443

插入：'xxxxx'到表'vvvvvvvv'，但只有'ccccc'并且没有指定员工ID的记录 –

虽然是1？ – user959443

在插入sql数据库之前检查现有记录

回答

相关问题