Oracle "ORA-01008: not all variables bound" Error w/ Parameters

Question

This is the first time I've dealt with Oracle, and I'm having a hard time understanding why I'm receiving this error.

I'm using Oracle's ODT.NET w/ C# with the following code in a query's where clause:

WHERE table.Variable1 = :VarA
  AND (:VarB IS NULL OR table.Variable2 LIKE '%' || :VarB || '%')
  AND (:VarC IS NULL OR table.Variable3 LIKE :VarC || '%')

and I'm adding the parameter values like so:

cmd.Parameters.Add("VarA", "24");
cmd.Parameters.Add("VarB", "test");
cmd.Parameters.Add("VarC", "1234");

When I run this query, the server returns:

ORA-01008: not all variables bound

If I comment out either of the 'AND (....' lines, the query completes successfully.

Why would the query run through alright if I'm only querying with two parameters, but not with three? The error I'm receiving doesn't even make sense

Answer 1

It seems daft, but I think when you use the same bind variable twice you have to set it twice:

cmd.Parameters.Add("VarA", "24");
cmd.Parameters.Add("VarB", "test");
cmd.Parameters.Add("VarB", "test");
cmd.Parameters.Add("VarC", "1234");
cmd.Parameters.Add("VarC", "1234");

Certainly that's true with Native Dynamic SQL in PL/SQL:

SQL> begin
  2     execute immediate 'select * from emp where ename=:name and ename=:name'
  3     using 'KING';
  4  end;
  5  /
begin
*
ERROR at line 1:
ORA-01008: not all variables bound


SQL> begin
  2     execute immediate 'select * from emp where ename=:name and ename=:name' 
  3     using 'KING', 'KING';
  4  end;
  5  /

PL/SQL procedure successfully completed.

Answer 2

The ODP.Net provider from oracle uses bind by position as default. To change the behavior to bind by name. Set property BindByName to true. Than you can dismiss the double definition of parameters.

using(OracleCommand cmd = con.CreateCommand()) {
    ...
    cmd.BindByName = true;
    ...
}