Exception thrown: 'system.data.oledb.oledbexception' in system.data.dll system.data.oledb.oledbexception (0x80040e14): syntax error (missing operator) in query expression

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I am practicing my own project, but I have syntax error that I can't figure it out.
This is Course Class that has courseID, courseName, description, and creditHour properties. DBSetup() method is connecting to the database. InsertDB() method is inserting the 4 values into the database.
CourseID, CourseName, Description are strings. CreditHour is int.

public string cmd;

public void InsertDB()
        {
            DBSetup();

            cmd = "INSERT into Patient values(" + getCourseID() + "," +
                             "'" + getCourseName() + "'," +
                             "'" + getDescription() + "'," +
                             getCreditHour() + ")";


            OleDbDataAdapter2.InsertCommand.CommandText = cmd;
            OleDbDataAdapter2.InsertCommand.Connection = OleDbConnection2;
            Console.WriteLine(cmd);

            try
            {
                OleDbConnection2.Open();
                int n = OleDbDataAdapter2.InsertCommand.ExecuteNonQuery();

                if (n == 1)
                    Console.WriteLine("Data Inserted...");
                else
                    Console.WriteLine("ERROR: Inserting Data");
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
            }
            finally
            {
                OleDbConnection2.Close();
            }
        } // end InsertDB()

What I have tried:

I think the syntax of the string cmd is wrong. I may put quotes and double qoutes wrong way. I was trying to figure this out for hours and hours. I cannot figure this out.

Posted 24-Sep-18 9:14am

Member 13996041

Updated 24-Sep-18 10:18am

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2 solutions

Solution 2

The second best thing about doing it correctly (use parameters, not concatenated strings) is that you don't have to worry about all the quotes and single quotes; and it makes it a lot cleaner and easier to check the values.

Five minutes of my time went into this parameterized version:

C#

cmd = "INSERT into Patient values(@CourseID, @CourseName, @Description, @CreditHour)";
 
string CourseID = getCourseID();
string CourseName = getCourseName();
string Description = getDescription();
int CreditHour = getCreditHour();

// insert breakpoint somewhere in here to check the incoming values

OleDbDataAdapter2.InsertCommand.CommandText = cmd;
OleDbDataAdapter2.InsertCommand.Connection = OleDbConnection2;
OleDbDataAdapter2.InsertCommand.Parameters.AddWithValue("@CourseID", CourseID);
OleDbDataAdapter2.InsertCommand.Parameters.AddWithValue("@CourseName", CourseName);
OleDbDataAdapter2.InsertCommand.Parameters.AddWithValue("@Description", Description);
OleDbDataAdapter2.InsertCommand.Parameters.AddWithValue("@CreditHour", CreditHour);

Posted 24-Sep-18 10:19am

MadMyche

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Patrice T · Accepted Answer · 2018-09-24T09:42:00

Quote:
but I have syntax error that I can't figure it out.

The syntax of your query depend on the value of CourseName and Description, a simple apostrophe in those fields is enough to completely change the syntax. That problem is 'SQL Injection'.

C#

cmd = "INSERT into Patient values(" + getCourseID() + "," +
"'" + getCourseName() + "'," + "'" + getDescription() + "'," + getCreditHour() + ")";

Never build an SQL query by concatenating strings. Sooner or later, you will do it with user inputs, and this opens door to a vulnerability named "SQL injection", it is dangerous for your database and error prone.
A single quote in a name and your program crash. If a user input a name like "Brian O'Conner" can crash your app, it is an SQL injection vulnerability, and the crash is the least of the problems, a malicious user input and it is promoted to SQL commands with all credentials.
SQL injection - Wikipedia[^]
SQL Injection[^]
SQL Injection Attacks by Example[^]
PHP: SQL Injection - Manual[^]
SQL Injection Prevention Cheat Sheet - OWASP[^]
How can I explain SQL injection without technical jargon? - Information Security Stack Exchange[^]