Programming with Access? Know this about "No value given for one or more required parameters"

Today, it’s more about programming .NET with an Access database. Last time, I explained the unique way Access handles JOIN. This time, let’s talk about a syntax error that masquerades as a missing parameter.

Suppose you have this code:

public void Foo()

{
string sql = "select bar from baz where quux is null";
 OleDbCommand cmd = new OleDbCommand(sql);
 // SET cmd.Connection TO A VALID OLEDBCONNECTION OBJECT HERE.
 cmd.ExecuteReader(); // Output is wasted, irrelevant to example
}

If you happen to have a table or view named baz with columns named bar and quux, this will work just fine. If, however, that table doesn’t exist, you’ll get an error reading “Table baz not found.”

Hah. You wish!

No, the actual error you get is “No value given for one or more required parameters.” This occurs even when your statement is not (intentionally) parameterized. It’s confusing the first few times, but the OLEDB driver follows this sort of logic:

  • Any identifier in a SQL statement is potentially a replaceable parameter.
  • But it could also be the name of a table, view, or column.
  • So if an identifier appears where a table or view makes sense, and it matches an existing table or view, there you go.
  • Ditto for a column name.
  • If there’s no match, the user must have intended a replaceable parameter.

And since you didn’t intend that, you never loaded the OleDbCommand object with parameter values, thus the error.

Of course the exact same thing occurs if instead of giving an incorrect or mispelled table name, you do the same with a column name.

I don’t know how to fix this.

My only suggestion, if this happens to you, is simply to be aware of what that error message really means. If you can’t figure out what is wrong with your SQL statement, try simplifying the statement a little bit at a time until it works. Whatever you took out last must have been the errant identifier. Or if the statement is rather complicated, go at it the other way and start with the simplest possible SQL and keep adding stuff back in until the error occurs.

And back to you

Have you used Access with OLEDB and .NET? What was it like? What kind of problems did you have? What else can you share about it? The comment section is yours.

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