OleDbDataReader说它正在读取的表中没有数据(VB.NET)

My OleDb access database connection correctly counts the number of rows (entries) in a table in the database, but when it comes to reading every instance of one of the fields using a for loop, I get the error that when getting the username (teacher_id/student_id) of the first entry in the table using databaseReader, there is no data in the databaseReader(1) instance.My OleDb access database connection correctly c