Go sql 从扫描返回多行

Question

我正在使用 Postgresql 数据库。 这是我要返回多行的代码块：

type NewsPaper struct {
    language string
    logo_url string
    slug string
    ranking string
    title string
    search_term string
}

func GetNewsPapers()  []byte{
    db := GetDB()
    newspaper := NewsPaper{}
    var json = jsoniter.ConfigCompatibleWithStandardLibrary

    rows, err := db.Query(`SELECT title, language, ranking, slug, search_term, logo_url FROM public.news_newspaper`)
    if err != nil {
        log.Println(err)
    }

    defer rows.Close()
    //results := []NewsPaper  // error : type []NewsPaper is not an expression
    for rows.Next() {

        err = rows.Scan(&newspaper.title, &newspaper.language, &newspaper.ranking, &newspaper.slug, &newspaper.search_term, &newspaper.logo_url)
        if err != nil {
            log.Println(err)
        }
        //results = append(results, newspaper)
    }
    fmt.Println(newspaper)  // printing last row
    err = rows.Err()
    if err != nil {
        panic(err)
    }
    values, _ := json.Marshal(newspaper)
    //fmt.Println(values)

    return values
}

问题是它从表中返回最后一行。 我也尝试将结果存储在数组中，但我没有成功。

Answer 1

您为每一行设置相同的结构变量，这就是为什么您只获取最后一行信息。

使用results:= []NewsPaper{}创建空切片并为每一行创建新结构。 这应该可行，我添加了一些评论。

rows, err := db.Query(`SELECT title, language, ranking, slug, search_term, logo_url FROM public.news_newspaper`)
if err != nil {
    log.Println(err)
}
results := []NewsPaper{} // creating empty slice
defer rows.Close()
for rows.Next() {
    newspaper := NewsPaper{} // creating new struct for every row
    err = rows.Scan(&newspaper.title, &newspaper.language, &newspaper.ranking, &newspaper.slug, &newspaper.search_term, &newspaper.logo_url)
    if err != nil {
        log.Println(err)
    }
    results = append(results, newspaper) // add new row information
}
fmt.Println(results)  // printing result

Answer 2

基本 CRUD 的另一种方法

import (
    "github.com/jmoiron/sqlx"
    "context"
)


type NewsPaper struct {
    Language   string `json:"language" db:"language"`
    LogoURL    string `json:"logo_url" db:"logo_url"`
    Slug       string `json:"slug" db:"slug"`
    Ranking    string `json:"ranking" db:"ranking"`
    Title      string `json:"title" db:"title"`
    SearchTerm string `json:"search_term" db:"search_term"`
}

type NewsPaperRepository interface {
    List(ctx context.Context) ([]NewsPaper, error)
}

type newsPaperRepository struct {
    db *sqlx.DB
}

func (r *newsPaperRepository) List(ctx context.Context) ([]NewsPaper, error) {

    const selectQuery = `SELECT title, language, ranking, slug, search_term, logo_url FROM public.news_newspaper`
    var newsPapers []NewsPaper
    if err := r.db.SelectContext(ctx, &newsPapers, selectQuery); err != nil {
        return nil, fmt.Errorf("news paper repository/problem while trying to retrieve news papers from database: %w", err)
    }
    return newsPapers, nil
}