如果存在于 sqflite flutter 中，则删除表并重新创建

Question

如果存在，我想在填充服务器数据之前删除表。

我正在尝试的查询

 deleteOptionTable() async {
    final db = await database;
    db.rawDelete("Delete * from option");
  }
  dropTable() async {
    final db = await database;
    db.query('SELECT * FROM cloudnet360.db WHERE name =option and type=table');
  }

我试过这样的事情，但没有发生任何事情。

void _insertOption(OptionsGroupList option) async {

    int idd =  dbHelper.dropTable();

    print('DROP TABLE: $idd');

    PreferencesConnector myprefs= PreferencesConnector();
    String merchantid=await myprefs.readString('merchantid');
    String hashkey=await myprefs.readString('hashkey');

    Map<String, dynamic> row = {
      DatabaseHelper.columnGroupId:option.grouprowid ,
      DatabaseHelper.columnGroupName: option.groupname,
      DatabaseHelper.columnIsRequired:option.isrequired ,
      DatabaseHelper.columnMerchantId: merchantid,
      DatabaseHelper.columnMerchantHashKey: hashkey,
    };
    int id = await dbHelper.insertOption(row);

    print('inserted option row id: $id');
  }

Answer 1

事实上，您的 dropTable 方法似乎实际上并未删除任何表：

要删除（删除）表：

DROP TABLE IF EXISTS my_table

清除表格内容：

DELETE FROM my_table

Answer 2

正如问题中所问的那样，我们需要一种方法来删除表（如果存在）并在颤振中重新创建它并使用 sqflite 包...

Future<void> DropTableIfExistsThenReCreate() async {

    //here we get the Database object by calling the openDatabase method 
    //which receives the path and onCreate function and all the good stuff
    Database db = await openDatabase(path,onCreate: ...);

    //here we execute a query to drop the table if exists which is called "tableName"
    //and could be given as method's input parameter too
    await db.execute("DROP TABLE IF EXISTS tableName");

    //and finally here we recreate our beloved "tableName" again which needs
    //some columns initialization
    await db.execute("CREATE TABLE tableName (id INTEGER, name TEXT)");

}