Unable to query data using c#

Question

I have three tables course, texts and book_adoption. I am getting an error when i am executing the following code-

connect();
            string qstr = "select course_id, book_isbn, book_title from texts natural join Book_Adoption natural join course where exists(select count(book_isbn) from Book_Adoption natural join course group by dept having count(course_id)>1) order by book_title";
            da = new OleDbDataAdapter(qstr, con);
            ds = new DataSet();
            da.Fill(ds, "course");
            //da.Fill(ds, "Texts");
            //da.Fill(ds, "Book_Adoption");
            dt = ds.Tables[0];
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                listBox1.Items.Add(dt.Rows[i]["course_id"].ToString());
                listBox1.Items.Add(dt.Rows[i]["book_isbn"].ToString());
                listBox1.Items.Add(dt.Rows[i]["book_title"].ToString());
            }

I am getting an error in the line da.Fill(ds, "texts"); When I am not using a natural join and doing a simple query, I am getting the correct output. WHat is wrong with the code?

OleDbException was unhandled IErrorInfo.GetDescription failed with E_FAIL(0x80004005). — pb_
– pb_, Commented Feb 21, 2012 at 10:45
when i do that i am getting this error- Value cannot be null. Parameter name: dataTable — pb_
– pb_, Commented Feb 21, 2012 at 10:47
What is about the joins that causes problems? I'm not familiar with natural joins but is there a case of primary keys not being set? If you run the query on Access directly does it work? — Daniel Hollinrake
– Daniel Hollinrake, Commented Feb 21, 2012 at 10:49

Nanhydrin · Accepted Answer · 2012-02-21 11:00:38Z

1

I think it might be this bit of your SQL query

(select count(book_isbn) from Book_Adoption

You're selecting a count not a column and this may be causing a problem because it doesn't know the column name.
See here for a similar scenario.

edited Feb 21, 2012 at 11:00

answered Feb 21, 2012 at 10:49

Nanhydrin

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Daniel Hollinrake Over a year ago

Following on from the answer Nanhydrin makes. Can you run this query in Access with no errors: "select course_id, book_isbn, book_title from texts natural join Book_Adoption natural join course where exists(select count(book_isbn) from Book_Adoption natural join course group by dept having count(course_id)>1) order by book_title"

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