create table命令文本mysql用户自定义c＃.net [英] create table command text mysql user defined c#.net

问题描述

我对此代码有疑问。我尝试根据用户在c＃.net框架中定义的数据库创建表。

I'm having problem regarding this code. I try to create table based on database that user defined in c#.net framework.

SchemaName schemaForm = new SchemaName();
            frmMetCon form2 = new frmMetCon();

            if (schemaForm.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
               
              string connStr = "datasource=localhost;port=3306;username=root;password=root;";
              MySqlConnection conn = new MySqlConnection(connStr);
                try
                 {
                   MySqlCommand command = conn.CreateCommand();
                   conn.Open();
                   command.CommandText = "DROP DATABASE IF EXISTS " + schemaForm.getData();
                   command.ExecuteNonQuery();
                   command.CommandText = "CREATE DATABASE " + schemaForm.getData();
                   command.CommandText = "CREATE TABLE Metabolites(MetaboliteID VARCHAR(10) NOT NULL, Metabolite_Name VARCHAR(45) NULL, ReactionTime INT NULL, PRIMARY KEY (MetaboliteID)";
                   command.ExecuteNonQuery();
                   this.Hide();
                   form2.Show();   
                 }
                 catch (Exception ex)
                 {
                   MessageBox.Show(ex.Message); 
                 }
                 conn.Close();
           
             }

错误显示没有选择数据库。如果我这样创建

The error showing that no database selected. if I create like this

command.CommandText = "CREATE TABLE" +schemaForm.getData()+ ".Metabolites(MetaboliteID VARCHAR(10) NOT NULL, Metabolite_Name VARCHAR(45) NULL, ReactionTime INT NULL, PRIMARY KEY (MetaboliteID)";

我的命令会出错。请帮助

I will get error on the command. Please help

推荐答案

我认为你的连接字符串有问题

检查以下 MySQL连接字符串

I think you have a problem with your connection string
check the following MySQL connection strings

在执行Create table命令之前，必须执行create database命令，比如

Before you execute the Create table command you must execute the create database command, Like

try
                {
                  MySqlCommand command = conn.CreateCommand();
                  conn.Open();
                  command.CommandText = "DROP DATABASE IF EXISTS " + schemaForm.getData();
                  command.ExecuteNonQuery();
                  command.CommandText = "CREATE DATABASE " + schemaForm.getData();
                    command.ExecuteNonQuery();
                  command.CommandText = "CREATE TABLE Metabolites(MetaboliteID VARCHAR(10) NOT NULL, Metabolite_Name VARCHAR(45) NULL, ReactionTime INT NULL, PRIMARY KEY (MetaboliteID)";
                  command.ExecuteNonQuery();
                  this.Hide();
                  form2.Show();
                }

SchemaName schemaForm = new SchemaName();
            frmMetCon form2 = new frmMetCon();
 
            if (schemaForm.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
               
              string connStr = "datasource=localhost;port=3306;username=root;password=root;";
              MySqlConnection conn = new MySqlConnection(connStr);
                try
                 {
                   MySqlCommand command = conn.CreateCommand();
                   conn.Open();
                   command.CommandText = "DROP DATABASE IF EXISTS " + schemaForm.getData();
                   command.ExecuteNonQuery();
                   command.CommandText = "CREATE DATABASE " + schemaForm.getData();
                   command.ExecuteNonQuery();
                   command.CommandText = "USE " + schemaForm.getData();
                   command.ExecuteNonQuery();
                   command.CommandText = "CREATE TABLE Metabolites(MetaboliteID VARCHAR(10) NOT NULL, Metabolite_Name VARCHAR(45) NULL, ReactionTime INT NULL, PRIMARY KEY (MetaboliteID)";
                   command.ExecuteNonQuery();
                   this.Hide();
                   form2.Show();   
                 }
                 catch (Exception ex)
                 {
                   MessageBox.Show(ex.Message); 
                 }
                 conn.Close();
           
             }

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