flutter_fetch_grammar.dart

  Future<List<GrammarItem>> getGrammarItemList({String categoryName = "", GrammarLevel grammarLevel = GrammarLevel.ALL}) async {
    await initDB();

    var query = """
    select grammar.grammar_id, grammar.grammar_name, grammar.grammar_category, grammar.grammar_level, grammar_desc.desc_en, grammar_structure.structure_en
    from grammar 
    inner join grammar_desc on grammar.grammar_id = grammar_desc.grammar_id
    inner join grammar_structure on grammar.grammar_id = grammar_structure.grammar_id
    """;

    if (categoryName != "") {
      query += 'where grammar_category like "%$categoryName%"';
    }

    if (grammarLevel != GrammarLevel.ALL) {

      String level = grammarLevel.toString().split('.').last;
      query += 'where grammar_level like "$level"';
    }

    try {
      List<Map> maps = await _grammarDb.rawQuery(query);
      return maps.map((rowData) => GrammarItem.fromMap(rowData)).toList();
    } catch (e) { }

    return [];
  }