SQL Reader上的类型不匹配异常

Question

When trying to read from my access db file in C# I get a

"Datatype mismatch in criteria expression" -> system.data.oledb.oledbexception (0x80040e07).

The code I'm trying to use is

public static void readHW(OleDbConnection connection, string article, string HWRev)
{            
   OleDbCommand ReadHW = new OleDbCommand($"SELECT * FROM [HW_Revision] WHERE [Article_ID] = {article} AND HW_Revision_ID = {HWRev}");          
   ReadHW.Connection = connection;
   OleDbDataReader reader = null;
   try
   {
      reader = ReadHW.ExecuteReader();
   }
   catch (Exception e)
   {
      Console.WriteLine(e);
   }
}

This is an adaption of my earlier python code with this SQL cmd

HW_RevrTest = cur.execute("""SELECT * FROM HW_Revision WHERE Article_ID = ? AND HW_Revision_ID = ?""", [Article, HWRev]).fetchall()

Answer 1

It's a while since I've done Access to be certain, but you don't seem to be passing your parameter values into the query at any point. Fix that and I'd hope it'd work.

Answer 2

Your python code was a parameterized query , where the database takes care of correct parameter usage.

But this: {article} is (I assume) a simple variable substitution, where you end up with SQL like

WHERE [Article_ID] = asdf4711

which is invalid for strings.

You can either use apostrophes

"SELECT * FROM [HW_Revision] WHERE [Article_ID] = '{article}' AND HW_Revision_ID = '{HWRev}'"

or better: use an actual parameterized OLEDB query .

Answer 3

string  query = "SELECT * FROM HW_Revision WHERE Article_ID =" + article  + " AND HW_Revision_ID = " + HWRev;

var HW_RevrTest = cur.execute(query);