Question

我通过这种方式使用关系填充来自多个表的数据集：

private void UcitajZahtjeve()
    {
        string query1 = "SELECT tblrezgo.IDRadnik, CONCAT(tblradnik.Ime, ' ', tblradnik.Prezime) AS ImePrezime, tblrezgo.EmailRadnik, tblrezgo.creationTime, tblrezgo.IDUnos ";
        query1 += "FROM tblrezgo ";
        query1 += "LEFT JOIN tblradnik ON tblradnik.IDRadnik = tblrezgo.IDRadnik ";
        query1 += "LEFT JOIN tblrezgolog ON tblrezgolog.IDUnos = tblrezgo.IDUnos ";
        query1 += "WHERE (tblrezgolog.OdobrenoN=1 AND tblrezgolog.OdobrenoHR=1) ";
        query1 += "ORDER BY tblrezgo.creationTime ASC";

        string query2 = "SELECT IDUnos, DatumGO, OdobrenoN, OdobrenoHR FROM tblrezgolog";

        gridZahtjevi.DataSource = dbTwoTableRelation(query1, query2, "Detalji", "IDUnos", "IDUnos").Tables[0];
        gridZahtjevi.LevelTree.Nodes.Add("Detalji", gridDetails);
    }

private DataSet dbTwoTableRelation(string query1, string query2, string relationName, string fieldName1, string fieldName2)
        {
        MySqlDataAdapter table1;
        MySqlDataAdapter table2;

        DataSet myDataSet = new DataSet();

        table1 = new MySqlDataAdapter(query1, this.connection);
        table2 = new MySqlDataAdapter(query2, this.connection);

        table1.Fill(myDataSet, "mainList");
        table2.Fill(myDataSet, "subList");

        myDataSet.Relations.Add(relationName, myDataSet.Tables["mainList"].Columns[fieldName1], myDataSet.Tables["subList"].Columns[fieldName2]).Nested = true;

      return myDataSet;

    }

查询工作正常，但如果我运行此代码，即使应用程序加载网格为空，我也会收到错误。

类型＆＃39; System.ArgumentException＆＃39;的第一次机会异常。发生了在System.Data.dll
中

如果我从query1中删除一个join子句，那么everthing就可以了。我不明白是什么原因导致问题，两个连接是否有问题？！

Answer 1

只需在运行时获取构造的query1并尝试在数据库中执行，然后很容易找到错误

Answer 2

使用查询像这样。它应该工作。

     string query1 = "SELECT tblrezgo.IDRadnik, CONCAT(tblradnik.Ime, ' ',   
                     tblradnik.Prezime) AS ImePrezime, tblrezgo.EmailRadnik, 
                     tblrezgo.creationTime, tblrezgo.IDUnos ";
                     query1 += "FROM tblrezgo ";
                     query1 += "LEFT JOIN tblradnik ON tblradnik.IDRadnik =  
                     tblrezgo.IDRadnik , tblrezgo  ";
                     query1 += "LEFT JOIN tblrezgolog ON tblrezgolog.IDUnos =  
                     tblrezgo.IDUnos ";
                     query1 += "WHERE (tblrezgolog.OdobrenoN=1 AND 
                     tblrezgolog.OdobrenoHR=1) ";
                     query1 += "ORDER BY tblrezgo.creationTime ASC";

DataSet与查询中的多个连接的关系

2 个答案: