Question

我想制作2个表：团队和项目我想在这两者之间建立1：n的关系。这是我的代码： // Creare tabela Projects

    public void CreareTabelaProjects() {
        string query = "CREATE TABLE IF NOT EXISTS Projects" + "(" + "id_project MEDIUMINT PRIMARY KEY AUTO_INCREMENT," + "name VARCHAR(30)," +
            "description VARCHAR(30)," + "FOREIGN KEY (team_id) REFERENCES Teams(team_id)" + ");";
        if (this.OpenConnection() == true) {
            MySqlCommand cmd = new MySqlCommand(query, connection);
            cmd.ExecuteNonQuery();
            this.CloseConnection();
        }
    }

   //Creare tabela Teams

    public void CreareTabelaTeams() {
        string query = "CREATE TABLE IF NOT EXISTS Teams" + "(" + "team_id INT AUTO_INCREMENT PRIMARY KEY," + "name VARCHAR(30)" + ");";
        if (this.OpenConnection() == true)
        {
            MySqlCommand cmd = new MySqlCommand(query, connection);
            cmd.ExecuteNonQuery();
            this.CloseConnection();
        }

    }

当我运行此时，发生错误说：关键栏＆＃39; team_id＆＃39;表格中不存在。应用程序仅创建Team表。有什么帮助吗？谢谢！

Answer 1

在第一个表之前创建第二个表

Answer 2

这是Project Table

的正确查询

 string query = "CREATE TABLE IF NOT EXISTS Projects" + "(" + "project_id INT AUTO_INCREMENT PRIMARY KEY," + "team_id INT,"+"name VARCHAR(30)," +
            "description VARCHAR(30)," + "FOREIGN KEY (team_id) REFERENCES Teams(team_id)" + ");";

非常感谢

使用外键在c＃中定义两个表

2 个答案: