SQL with Visual C#: Incorrect syntax near ''

Question

I keep on getting an sql exception error that states:

Incorrect syntax near 'Bsc.'.

This error happens at the line I have indicated with a comment.

'Bsc' is the value of val1 that has been parsed?

I have tried all means to resolve the error but I am not sure what's the problem,

public Marksheet(object val1, object val2, object val3, object val4)
{
    InitializeComponent();

    string connectionString = null;
    SqlConnection conn; 
    connectionString = "Server=localhost\\SQLEXPRESS;Integrated security=SSPI;database=jms";

    SqlDataAdapter sda = new SqlDataAdapter("Select s.course_abbreviation, s.course_name, s.month_of_admission, s.year_of_admission from students s where exists (select 1 from units_allocation ua where s.course_abbreviation=ua.'"+val1+"' and s.course_name=ua.'"+val2+"' and s.month_of_admission=ua.'"+val3 +"' and s.year_of_admission=ua.'"+val4+"'", connectionString);

    conn = new SqlConnection(connectionString);
    DataTable dt5 = new System.Data.DataTable();
    sda.Fill(dt5);    // Error occurs here
    gridControl1.DataSource = dt5;
}

The sql query is an inner join between students table and units_allocated table.

I am fetching records from students table where the 4 fields are equal...

The above function is in different form and which is called by the following:

object val1;
    object val2;
    object val3;
    object val4;
    private void gridView1_RowClick(object sender, RowClickEventArgs e)
    {
        int rowHandle = e.RowHandle;
        val1 = gridView1.GetRowCellValue(rowHandle, gridView1.Columns[2]);
        val2 = gridView1.GetRowCellValue(rowHandle, gridView1.Columns[3]);
        val3 = gridView1.GetRowCellValue(rowHandle, gridView1.Columns[4]);
        val4 = gridView1.GetRowCellValue(rowHandle, gridView1.Columns[5]);

        Marksheet marksheet = new Marksheet(val1, val2, val3, val4);
        marksheet.Show();
    }

I want to output a gridview/table in the second form with student records having 4 field values to the one I am clicking.

I am passing column values and expecting records from students table with fields registration_no, first_name, last_name, cat1_marks, cat2_marks, exam_marks and overall_marks.

Answer 1

It seems you are trying to match on column names and your val variables contain the names of those columns, so you need to remove the single quotes - the quotes are only necessary if trying to match on an explicit value.

where s.course_abbreviation=ua."+val1+"

so your query will look like this:

SqlDataAdapter sda = new SqlDataAdapter(
"Select s.course_abbreviation, s.course_name, s.month_of_admission, s.year_of_admission " + 
"from students s " + 
"where exists (select 1 from units_allocation ua " +
"where s.course_abbreviation=ua."+val1+" and s.course_name=ua."+val2+" and s.month_of_admission=ua."+val3 +" and s.year_of_admission=ua."+val4+""
, connectionString);

Of course the usual "you should never inject SQL parameters that way!" warning applies.

---

Edit:

if my previous assumption was incorrect, then the other issue you have is the table alias in your where clause - just remove it. But if you do that then your inner select still looks really wrong*. If we distill it down to just a straight SQL statement we have:

select s.course_abbreviation, s.course_name, s.month_of_admission, s.year_of_admission  
from students s 
where exists (
                 select 1 
                 from units_allocation ua 
                 where s.course_abbreviation='val1' 
                 and s.course_name='val2' 
                 and s.month_of_admission='val3' 
                 and s.year_of_admission='val4'
             )

This is a bit of a funny way to try to do an inner join. Why would you select from the units_allocation table by comparing students columns to explicit values?

You may be stuck because there is no direct link from units_allocation back to students, - in this case you will need to join via other tables as well. Your inner join should look something like this:

select s.*, ua.*
from students s
    inner join units_allocation ua
    on ua.[foreign_key_column] = s.[primary_key_column]
where s.course_abbreviation='val1'
and s.course_name='val2'
...etc...

Using an exists could be counterproductive the way you have it - it will return all rows in the outer query if the exists condition is satisfied.

*_{I'm a SQL generalist, not a specialist. So this exists() syntax for achieving an inner join may be totally wrong, I don't know unless I try it - which I haven't (and I've never written a join in that way).}

Answer 2

where s.course_abbreviation=ua.'"+val1+"'

Remove the ua. and it should fix it.

using x. in front of a variable in SQL tries to find the defination of a column.