Golang实现mysql where in 查询

一、第一种写法

首先说一下遇到的一个问题

sql: converting argument $1 type: unsupported type []int, a slice of int

以下代码是最初遇到问题的代码

package controllers

import (
    "fmt"
    "github.com/astaxie/beego"
    "mypro/models"
    "strings"
)

type GetMovieInfoController struct {
    beego.Controller
}
type MovieInfo struct {
    Id                   int64
    Movie_name           string
    Movie_director       string
}


func placeholders(n int) string {
    var b strings.Builder
    for i := 0; i < n - 1; i++ {
        b.WriteString("?,")
    }
    if n > 0 {
        b.WriteString("?")
    }
    return b.String()
}

func (c *GetMovieInfoController)  Get() {
    ids := []int{5,6,7}
    db := models.ConnectDb();
    defer db.Close()
    query := fmt.Sprintf("select id,movie_name ,movie_director from movie_info where id in (%s)", placeholders(len(ids)))
    rows, err := db.Query(query,ids)
    fmt.Fprint(c.Ctx.ResponseWriter, rows)
    fmt.Fprint(c.Ctx.ResponseWriter, ids)
    fmt.Fprint(c.Ctx.ResponseWriter, err)


}

解决方案

package controllers

import (
    "fmt"
    "github.com/astaxie/beego"
    "mypro/models"
    "strings"
)

type GetMovieInfoController struct {
    beego.Controller
}
type MovieInfo struct {
    Id                   int64
    Movie_name           string
    Movie_director       string
}


func placeholders(n int) string {
    var b strings.Builder
    for i := 0; i < n - 1; i++ {
        b.WriteString("?,")
    }
    if n > 0 {
        b.WriteString("?")
    }
    return b.String()
}

func (c *GetMovieInfoController)  Get() {
    ids := []interface{}{5,6,7}  //这里使用interface关键字
    db := models.ConnectDb();
    defer db.Close()
    query := fmt.Sprintf("select id,movie_name,movie_director  from movie_info where id in (%s)", placeholders(len(ids)))
    rows, err := db.Query(query,ids...)  //加...  这里是解决了问题，但是实质性还不知道哈，基础入门阶段，以后再了解
    fmt.Fprint(c.Ctx.ResponseWriter, rows)
    fmt.Fprint(c.Ctx.ResponseWriter, ids)
    fmt.Fprint(c.Ctx.ResponseWriter, err)

    item := MovieInfo{}
    list := []MovieInfo{}
    for rows.Next(){
        var mid int64
        var movie_name, movie_director string
        err = rows.Scan(&mid,&movie_name,&movie_director)
        if err != nil {
            panic(err.Error())
        }
        item.Id = mid
        item.Movie_name = movie_name
        item.Movie_director = movie_director
        list = append(list,item)
    }
    fmt.Fprint(c.Ctx.ResponseWriter, list)

    fmt.Println(list)
}

 二、第二种写法

package controllers

import (
    "fmt"
    "github.com/astaxie/beego"
    "mypro/models"
)

type GetMovieInfoController struct {
    beego.Controller
}
type MovieInfo struct {
    Id                   int64
    Movie_name           string
    Movie_director       string
}


func formatids(ids []int) ([]interface{},string) {
    inIds := ""
    params:=make([]interface{},0)
    for i:=0;i<len(ids);i++{
        if i==0{
            inIds+="?"
        }else{
            inIds+=",?"
        }
        params=append(params , ids[i])
    }
    return params,inIds
}

func (c *GetMovieInfoController)  Get() {
    ids := []int{8,9,10}
    db := models.ConnectDb();
    defer db.Close()
    sql := "select id,movie_name,movie_director  from movie_info where id in (%s)"


    params,inIds := formatids(ids)

    sql = fmt.Sprintf(sql ,inIds )
    fmt.Fprint(c.Ctx.ResponseWriter,sql)
    rows,err := db.Query(sql , params...)

    fmt.Fprint(c.Ctx.ResponseWriter, rows)
    fmt.Fprint(c.Ctx.ResponseWriter, ids)
    fmt.Fprint(c.Ctx.ResponseWriter, err)


    item := MovieInfo{}
    list := []MovieInfo{}
    for rows.Next(){
        var mid int64
        var movie_name, movie_director string
        err = rows.Scan(&mid,&movie_name,&movie_director)
        if err != nil {
            panic(err.Error())
        }
        item.Id = mid
        item.Movie_name = movie_name
        item.Movie_director = movie_director
        list = append(list,item)
    }
    fmt.Fprint(c.Ctx.ResponseWriter, list)

    fmt.Println(list)
}

 三、第三种写法

func (c *GetMovieInfoController)  Get() {        
       ids := []string{"8", "9", "10"}
    
    db := models.ConnectDb();
    defer db.Close()


    idStr := strings.Join(ids, "','")
    fmt.Println(idStr)

    sqlText := "select id,movie_name,movie_director  from movie_info where id in  ('%s')"
    sqlText = fmt.Sprintf(sqlText, idStr)


    rows,err := db.Query(sqlText)  
}  

//sql
select id,movie_name,movie_director  from movie_info where id in  ('8','9','10')