UPDATE PreparedStatement不使用JDBC更新MSSQL

Question

I am trying to update a MSSQL instance using JDBC using a prepared statement, I made a method to update any record in the table when given the column name, the value to update, and the updated value.

public void updateProjectOptions(int projectID, int number, String column){
    try {
        PreparedStatement ps = conn.prepareStatement("UPDATE cryptic.dbo.projects SET ? = ? WHERE project_id = ?");
        int newNum = number+1;
        System.out.println(projectID+" "+newNum+" "+column);
        ps.setString(1, column);
        ps.setInt(2, newNum);
        ps.setInt(3, projectID);
        int debug = ps.executeUpdate();
        System.out.println("Rows affected: "+debug);
    } catch (SQLException ex) {
        Logger.getLogger(DAL.class.getName()).log(Level.SEVERE, null, ex);
    }
}

The first print statement is printing out the correct values so I know the inputs are correct, and the second print statement is letting me know that 1 row is affected which is correct.

If I run the script inside of Management Studio the script runs fine and updates the table, but if I run the script from the java project nothing is updated and no errors are generated.

The db table in question has 4 columns: (int)project_id, (nvarchar)project_name, (int)num_bugs, (int)num_features

Can anyone help me out with getting this to work and/or spot whats wrong?

Answer 1

You can't bind a column name that way, only variables.

I would recommend that you close that PreparedStatement in method scope in a finally block. Your way is asking for trouble.

I would also call writing to System.out a very bad idea. I'd prefer returning the number of affected rows to the user.

Answer 2

Column names cannot be parameterized in prepared statements. You can parameterize only literal values like strings or numbers.