[c#] ORA-01036: illegal variable name/number when running query through C#

I am trying to use ALTER USER query for Oracle database using OracleCommand in C# in the following code. It creates the query if the values for Username and password are not empty strings. But I get an error "ORA-01036: illegal variable name/number" when ExecuteNonQuery() is executed.

  string updateQuery = "ALTER USER :user IDENTIFIED BY :password";
  connection = new OracleConnection(LoginPage.connectionString);
  connection.Open();                
  OracleCommand cmd = new OracleCommand(updateQuery, connection);
  cmd.Connection = connection;  
  for(int i=0;i<usersList.Count;i++)
        {
            if (!(selectedUsersArray[i].Equals("")) && !passwordArray[i].Equals(""))
            {
                OracleParameter userName = new OracleParameter();
                userName.ParameterName = "user";
                userName.Value = selectedUsersArray[i];

                OracleParameter passwd = new OracleParameter();
                passwd.ParameterName = "password";
                passwd.Value = passwordArray[i];

                cmd.Parameters.Add(userName);
                cmd.Parameters.Add(passwd);

                cmd.Prepare();
                cmd.ExecuteNonQuery();                   


            }
        }

Could you please suggest what is wrong with my implementation?.

This error happens when you are also missing cmd.CommandType = System.Data.CommandType.StoredProcedure;

 cmd.Parameters.Add(new OracleParameter("GUSERID ", OracleType.VarChar)).Value = userId;

I was having eight parameters and one was with space at the end as shown in the above code for "GUSERID ".Removed the space and everything started working .

The Oracle error ORA-01036 means that the query uses an undefined variable somewhere. From the query we can determine which variables are in use, namely all that start with @. However, if you're inputting this into an advanced query, it's important to confirm that all variables have a matching input parameter, including the same case as in the variable name, if your Oracle database is Case Sensitive.

I was having the same problem in an application that I was maintaining, among all the adjustments to prepare the environment, I also spent almost an hour banging my head with this error "ORA-01036: illegal variable name / number" until I found out that the application connection was pointed to an outdated database, so the application passed two more parameters to the outdated database procedure causing the error.

You cannot pass user/table name to pl/sql with a parameter. You can create a procedure and build sql and then execute immediately to achieve that.

I have faced same problem ... For the problem is like this, I am calling the PRC inside cpp program and my PRC taking 4 arguments but while calling I used only 1 arguments so this error came for me.

Begin Example_PRC(:1); End; // this cause the problem 
Begin Example_PRC(:1,:2,:3,:4); End; // this is the solution

You defined one oracleCommand but used it in 'for'. it means you are adding parameter with the same name to one OracleCommand. you should use cmd.Parameters.clear() to refresh your parameters.

for(int i=0;i<usersList.Count;i++)
        {
            if (!(selectedUsersArray[i].Equals("")) && !passwordArray[i].Equals(""))
            {
                cmd.Parameters.clear();//Add this line
                OracleParameter userName = new OracleParameter();
                userName.ParameterName = "user";
                userName.Value = selectedUsersArray[i];

                OracleParameter passwd = new OracleParameter();
                passwd.ParameterName = "password";
                passwd.Value = passwordArray[i];

                cmd.Parameters.Add(userName);
                cmd.Parameters.Add(passwd);

                cmd.Prepare();
                cmd.ExecuteNonQuery();                   


            }
        } 

The root cause

In Oracle you have three kinds of SQL statements (and additionally there are PL/SQL blocks):

• Statements in the Data Definiton Language (DDL). These statements modify the structure of the database. They begin usually with the verbs "ALTER" or "CREATE"
• Statements in the Data Modification Langugage (DML). There statements modify the content inside of tables, leaving the structure of each table unmodified. These statements usually begin with "INSERT", "MERGE" or "DELETE".
• Statements in what I call "query language" (there seems to be no canonical name for these). This statements start with the verb "SELECT".

Bind variables in Oracle are only allowed in some special places in DML and query statements. You are trying to use bind variables in a places where they are not allowed. Hence the error.

Solution

Build your statement without bind variables. Build the complete query string instead using string concatenation.

If you want to sanitize the input before concatenating the string, use the DBMS_ASSERT package.

Background

Bind variables can only be used when Oracle can build a query plan without knowing the value of the variable. For DDL statements, there is no query plan. Hence bind variables are not allowed.

In DML and query statements, bind variables are only allowed, when they are used inside a tuple (regarding the underlying set theory), i.e. when the value will be compared with the value in a table or when the value will be inserted in a table. They are not allowed to change the structure of the execution plan (e.g. to change the target table or to change the number of comparisons).

Just for others getting this error and looking for info on it, it is also thrown if you happen to pass a binding parameter and then never use it. I couldn't really find that stated clearly anywhere but had to prove it through trial and error.

I just spent several days checking parameters because I have to pass 60 to a stored procedure. It turns out that the one of the variable names (which I load into a list and pass to the Oracle Write method I created) had a space in the name at the end. When comparing to the variables in the stored procedure they were the same, but in the editor I used to compare them, I didnt notice the extra space. Drove me crazy for the last 4 days trying everything I could find, and changing even the .net Oracle driver. Just wanted to throw that out here so it can help someone else. We tend to concentrate on the characters and ignore the spaces. . .