Golang db.Query 与 sql join

Question

我想查询 aquestion及其所有answers. 以下两个函数工作得很好。问题是我认为这应该在一个函数中完成，一个查询。（为简洁起见，我删除了错误检查）。

func QuestionById(id string) (*Question, error) {
    question := new(Question)
    _ = db.QueryRow("select * from question where question.id = ?", id).Scan(
        &question.Id,
        &question.LessonId,
        &question.Body,
        &question.Type,
    )

    return question, nil
}

func AnswersByQuestionId(id string) ([]*Answer, error) {
    rows, _ := db.Query("select * from answer where question_id = ?", id)
    defer rows.Close()

    answers := make([]*Answer, 0)

    for rows.Next() {
        answer := new(Answer)

        _ = rows.Scan(&answer.Id, &answer.Body, &answer.QuestionId, &answer.Correct)

        answers = append(answers, answer)
    }
    _ = rows.Err()

    return answers, nil
}

我想以这种方式（或类似方式）使用连接查询：

func QuestionByIdAndAnswers(id string) (*Question, []*Answer error) {
    rows, _ := db.Query("select * from question join answer on question.id = answer.question_id where question.id = ?", id)

    // more stuff here

    return question, answers, nil
}

Answer 1

一般来说，它必须是这样的：

func QuestionByIdAndAnswers(id string) (*Question, []*Answer, error) {
  query := `
    SELECT q.id, q.body, a.id, a.question_id, a.body
    FROM question AS q
    JOIN answer AS a ON q.id = a.question_id
    WHERE q.id = ?
  `
  rows, err := db.Query(query, id)
  checkErr(err)

  question := &Question{}
  for rows.Next() {
    answer := &Answer{}
    err = rows.Scan(
      &question.ID,
      &question.Body,
      &answer.ID,
      &answer.QuestionID,
      &answer.Body,
    )
    checkErr(err)
    question.Answers = append(question.Answers, answer)
  }

  return question, question.Answers, nil
}

请注意，我特意替换了:
SELECT *toSELECT q.id, q.body, a.id, a.question_id, a.body
目的是为了避免诸如：
panic: sql: expected 6 destination arguments in Scan, not 5
在表中添加或删除某些列时可能发生的错误 ，因此此查询更加健壮。

这只是基本的实现，你可以用更多的领域扩展它......

PS：checkErr为简洁起见，也省略了函数。