RoomDbMigration2.kt

 val MIGRATION_3_4 = object : Migration(3, 4){
                        override fun migrate(database: SupportSQLiteDatabase) {
                            //create new table 
                            database.execSQL("CREATE TABLE `new_course_table`(`course_index_key` INTEGER NOT NULL," +
                                    " `course_code` TEXT NOT NULL," +
                                    " `course_title` TEXT NOT NULL, " +
                                    "`course_unit` INTEGER NOT NULL," +
                                    " `course_status` TEXT," +
                                    " `course_date_added` INTEGER," +
                                    " PRIMARY KEY(`course_index_key`) )")
                                    
                            //insert data from old table into new table        
                            database.execSQL("INSERT INTO new_course_table(course_code," +
                                    " course_title," +
                                    " course_unit," +
                                    " course_status," +
                                    " course_date_added)" +
                                    " SELECT course_code, course_title, course_unit, course_status, course_date_added  FROM course_table")
                        
                          //drop old table 
                          database.execSQL("DROP TABLE course_table")
                          
                          //rename new table to the old table name 
                          database.execSQL("ALTER TABLE new_course_table RENAME TO course_table")

                        }
                    }

Handling RoomDb Migration: Create a new primary key column in an existing entity