It was okay until I tried to upgrade it to add one more column to it - sql

Question

I was learning to use sqlflite in my flutter application..when i upgraded it for the first time it worked absolutely fine..but then I wanted to add one more column but i actually don't know query for that.. so I tried the query shown below, but when I try to save my data, I get this error:
E/SQLiteLog(22556): (1) table tbl_employee has no column named employee_gender
I/flutter (22556): DatabaseException(table tbl_employee has no column named employee_gender (code 1 SQLITE_ERROR): , while compiling: INSERT OR REPLACE INTO tbl_employee (employee_name, employee_Student, employee_depertment, employee_DOB, employee_gender) VALUES (?, ?, ?, ?, ?)) sql 'INSERT OR REPLACE INTO tbl_employee (employee_name, employee_Student, employee_depertment, employee_DOB, employee_gender) VALUES (?, ?, ?, ?, ?)' args [Adrita, teacher, CMT, 19/00/2020, 2]}
This is my database class:
class DBHelper{
static final String CREATE_TABLE_EMPLOYEE = '''
create table $TABLE_EMPLOYEE(
$COL_EMP_ID integer primary key autoincrement,
$COL_EMP_NAME text not null,
$COL_EMP_PROFESSION text not null,
$COL_EMP_DEPARTMENT text not null
)
''';
static Future<Database> open() async{// to initialize data we used this method
final dbpath = await getDatabasesPath();//directory
final path = Path.join(dbpath,'employee.db');//main Path
return openDatabase(path,version: 3,onCreate: (db, version) async{
await db.execute(CREATE_TABLE_EMPLOYEE);
}, onUpgrade: (db, oldVersion, newVersion) async{
if(newVersion == 2){
db.execute(''' alter table $TABLE_EMPLOYEE add column $COL_EMP_DOB text ''');
}
if(newVersion == 3){
db.execute('''alter table $TABLE_EMPLOYEE add column $COL_RADIO_BUTTON integer ''');
}
},);
}
static Future<int> insertEmployee(String table, Map<String, dynamic> map) async {// insert method
final db = await open();
return await db.insert(table, map, conflictAlgorithm: ConflictAlgorithm.replace);
}
static Future<int> updateEmployee(EmployeeTeacherModel employeemodel) async{
final db = await open();
return await db.update(TABLE_EMPLOYEE, employeemodel.toMap(), where: '$COL_EMP_ID = ?', whereArgs: [employeemodel.id]);
}
static Future<int> DeleteEmployee(int id) async{
final db = await open();
return await db.delete(TABLE_EMPLOYEE,where: '$COL_EMP_ID = ?', whereArgs: [id]);
}
static Future<List<EmployeeTeacherModel>> getAllEmployees() async{
final db = await open();
final List<Map<String, dynamic>> map = await db.query(TABLE_EMPLOYEE, orderBy: COL_EMP_NAME);
return List.generate(map.length, (index){
return EmployeeTeacherModel.fromMap(map[index]);
});
}
static Future<EmployeeTeacherModel> getEmployeeByid(int id) async{
final db = await open();
final List<Map<String, dynamic>> emps = await db.query(TABLE_EMPLOYEE, where: '$COL_EMP_ID=?',whereArgs: [id]);
if(emps.length>0){
return EmployeeTeacherModel.fromMap(emps.first);
}
return null;
}
}
Here's the Model class:
final String TABLE_EMPLOYEE = "tbl_employee";
final String COL_EMP_ID = "employee_id";
final String COL_EMP_NAME = "employee_name";
final String COL_EMP_DEPARTMENT = "employee_depertment";
final String COL_EMP_PROFESSION = "employee_Student";
final String COL_EMP_DOB = "employee_DOB";
final String COL_RADIO_BUTTON = "employee_gender";
class EmployeeTeacherModel {
int id;
String name;
String depertment;
String Dob;
String profession;
int gender;
EmployeeTeacherModel({this.id, this.name, this.depertment, this.profession, this.Dob, this.gender});
Map<String,dynamic> toMap(){//method to insert data into database
var map = <String, dynamic>{//method
COL_EMP_NAME : name,
COL_EMP_PROFESSION: profession,
COL_EMP_DEPARTMENT: depertment,
COL_EMP_DOB: Dob,
COL_RADIO_BUTTON: gender,
};
if(id !=null){
map[COL_EMP_ID] = id;
}
return map;
}
EmployeeTeacherModel.fromMap(Map<String,dynamic> map){//named constructor to return emoloyee model obj
id = map[COL_EMP_ID];
name = map[COL_EMP_NAME];
profession = map[COL_EMP_PROFESSION];
depertment = map[COL_EMP_DEPARTMENT];
Dob = map[COL_EMP_DOB];
gender = map[COL_RADIO_BUTTON];
}
#override
String toString() {
return 'EmployeeTeacherModel{id: $id, name: $name, depertment: $depertment, Dob: $Dob, profession: $profession, gender: $gender}';
}
}