This restriction cannot be enabled because not all values ​​have corresponding parent values.

I have three nested tables in a dataset. I show the data based on the language identifier, that is: EN - 1 FR - 2, and NL - 3. French and English exist in the database, but Dutch does not exist yet, and when the user selects NL, I get the following error:

This restriction cannot be included because not all values ​​have corresponding parent values.

Below is the code that I use to get the data. An error occurs when I try to create relationships in a dataset.

 (ds.Relations.Add(new DataRelation("Cat_SubCat", dk1, dk2));

Now my question is: how can I check if a value exists in a dataset or database with the given code below?

 public static DataTable GetData(Int32 languageID)
    {
        DataSet ds = new DataSet();

        string commandText = @"SELECT * FROM AlacarteCat where languageID = @ID;
                               SELECT * FROM AlacarteSubCat where languageID = @ID;
                               SELECT * from AlacarteItems where languageID = @ID";

        using (SqlConnection myConnection = new SqlConnection(Common.GetConnectionString("SQLConnectionString")))
        {
           SqlCommand command = new SqlCommand(commandText, myConnection);
            command.Parameters.Add("@ID", SqlDbType.Int);
            command.Parameters["@ID"].Value = languageID;

            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = command;
            da.TableMappings.Add("AlacarteCat", "AlacarteCat"); // table 0
            da.TableMappings.Add("AlacarteSubCat", "AlacarteSubCat"); // table 1
            da.TableMappings.Add("AlacarteItems", "AlacarteItems"); // table 2
            da.Fill(ds, "AlacarteCat");

            DataColumn dk1 = ds.Tables[0].Columns["ID"];
            DataColumn dk2 = ds.Tables[1].Columns["AlacarteCatID"];
            DataColumn dk3 = ds.Tables[1].Columns["ID"];
            DataColumn dk4 = ds.Tables[2].Columns["AlacarteSubCatID"];
            DataColumn dk5 = ds.Tables[0].Columns["id"];
            DataColumn dk6 = ds.Tables[2].Columns["AlacarteCatID"];
            ds.Relations.Add(new DataRelation("Cat_SubCat", dk1, dk2));
            ds.Relations.Add(new DataRelation("SubCat_Items", dk3, dk4));
            ds.Relations.Add(new DataRelation("Cat_Items", dk5, dk6));

            if ((ds != null))
            {
                return ds.Tables["AlacarteCat"];
            }
            return null;
        }

    }