sql - 过滤和排序 SQL 查询以重新创建嵌套结构

Question

我是 Go 的新手，我正在尝试从 SQL 查询填充一个名为 Reliefworker 的结构，我可以将其作为 JSON 负载发送。

本质上，我有一个 Reliefworker，他可能被分配到许多社区，而社区可以由多个区域组成。

我怀疑除了我想要的之外，还有一种聪明的方法可以做到这一点，这是一种原始解决方案，它将(通过社区)添加到 SQL 中并创建一个函数来检测所添加的社区是否与前一个，在这种情况下，我会创建一个新的社区结构类型对象来附加。

type Reliefworker struct {
    Name     string `json:"name"`
    Communities  []Community `json:"community"`
    Deployment_id    string `json:"deployment_id"`
 }

 type Community struct{
    Name     string `json:"name"`
    community_id     string `json:"community_id"`
    Regions []Region `json:"regions"`
}

type Region struct{
    Name     string `json:"name"`
    Region_id     string `json:"region_id"`
    Reconstruction_grant   string `json:"reconstruction_grant"`
    Currency string `json:"currency"`
}

目前我已经创建了一个结构，它反射(reflect)了我在考虑下一步行动时从 SQL 中实际得到的结果。也许这可能是一个很好的垫脚石，而不是尝试即时转换？

type ReliefWorker_community_region struct {
    Deployment_id        string
    Community_title      int
    Region_name          string
    Reconstruction_grant int
}

func GetReliefWorkers(deployment_id string) []Reliefworker {

    fmt.Printf("Confirm I have a deployment id:%v\n", deployment_id)

    rows, err := middleware.Db.Query("select deployment_id, community_title, region_name, reconstruction_grant WHERE Deployment_id=$1", brand_id)

    if err != nil {
        return
    }

    for rows.Next() {
        reliefworker := Reliefworker{}
        err = rows.Scan(&deployment_id, &community_title, &region_name, &reconstruction_grant)
        if err != nil {
            return
        }
    }
    rows.Close()

    return
}

Answer 1

我认为排序很有意义，原始解决方案可能是最有效的:

func GetReliefWorkers(deployment_id string) []Reliefworker {
    // Added sort to query
    q := "select worker_name, community_title, region_name, reconstruction_grant WHERE deployment_id=? ORDER BY community_title"    
    rows, err := middleware.Db.Query(q, deployment_id)
    if err != nil {
        return
    }
    defer rows.Close() // So rows get closed even on an error
    c := Community{} // To keep track of the current community
    cmatrix := [][]string{[]string{}}  // Matrix of communities and workers
    communities := []Community{} // List of communities
    workers := make(map[string]Reliefworker) // Map of workers
    var ccount int // Index of community in lists
    for rows.Next() {
        w := Reliefworker{Deployment_id: deployment_id}
        r := Region{}
        var ctitle string  // For comparison later
        err = rows.Scan(&w.Name, &ctitle, &r.Name, &r.Reconstruction_grant)
        if err != nil {
            return
        }
        if ctitle != c.Name {
            communities = append(communities, c)
            c = Community{}
            c.Name = ctitle
            ccount++
            cmatrix = append(cmatrix, []string{})
        }
        c.Regions = append(c.Regions, r)
        cmatrix[ccount] = append(cmatrix[ccount], w.Name)
        workers[w.Name] = w
    }
    for i, c := range communities {
        for _, id := range cmatrix[i] {
            w := workers[id] // To avoid error 
            w.Communities = append(w.Communities, c)
            workers[id] = w
        }
    }
    out := []Reliefworker{}
    for _, w := range workers {
        out = append(out, w)
    }
    return out
}

尽管为社区、地区和 worker 创建单独的表可能更有意义，然后使用JOIN查询它们:https://www.w3schools.com/sql/sql_join_inner.asp

更新:既然您只想找回一个Reliefworker，这样的事情行得通吗？

type ReliefWorker struct {
    Name        string      `json:"name"`
    Communities []Community `json:"community"`
}

type Community struct {
    Name    string   `json:"name"`
    Regions []Region `json:"regions"`
}

type Region struct {
    Name                 string `json:"name"`
    Region_id            string `json:"region_id"`
    Reconstruction_grant int    `json:"reconstruction_grant"`
    Currency             string `json:"currency"`
}

func GetReliefWorkers(deployment_id string) Reliefworker {
    reliefworker := Reliefworker{}
    communities := make(map[string]Community)
    rows, err := middleware.Db.Query("select name, community_title, region_name, region_id, reconstruction_grant WHERE Deployment_id=$1", deployment_id)
    if err != nil {
        if err == sql.ErrNoRows {
            fmt.Printf("No records for ReliefWorker:%v\n", deployment_id)
        }
        panic(err)
    }
    defer rows.Close()
    for rows.Next() {
        c := Community{}
        r := Region{}
        err = rows.Scan(&reliefworker.Name, &c.Name, &r.Name, &r.Region_id, &r.Reconstruction_grant)
        if err != nil {
            panic(err)
        }
        if _, ok := communities[c.Name]; ok {
            c = communities[c.Name]
        }
        c.Regions = append(c.Regions, r)
        communities[c.Name] = c
    }
    for _, c := range commmunities {
        reliefworker.Communities = append(reliefworker.Communities, c)
    }
    return reliefworker
}