英文:
Saving data to a file golang sql query
问题
帮助我，如何将接收到的数据写入文件？我需要将section_id和modified_by的所有数据写入文件。
rows, err := db.Query("select section_id, modified_by from enrollment where rownum < 5")
if err != nil {
fmt.Println("Error running query")
fmt.Println(err)
return
}
defer rows.Close()
var section_id string
var modified_by string
for cont := true; cont; cont = rows.NextResultSet() {
for rows.Next() {
err := rows.Scan(§ion_id, &modified_by)
if err != nil {
fmt.Println(err)
}
fmt.Println(section_id, modified_by)
// 在这里将数据写入文件
}
}
谢谢您的帮助！
英文:
Help me, pls. How can I write the received data on file? I need write all-data from section_id, modified_by.
rows, err := db.Query("select section_id, modified_by from enrollment where rownum < 5")
if err != nil {
fmt.Println("Error running query")
fmt.Println(err)
return
}
defer rows.Close()
var section_id string
var modified_by string
for cont := true; cont; cont = rows.NextResultSet() {
for rows.Next() {
err := rows.Scan(&section_id, &modified_by)
if err != nil {
fmt.Println(err)
}
fmt.Println(section_id, modified_by)
}
}
}
Thank you for any help!
答案1
得分: 0
用以下代码替换循环部分：
f, err := os.Create("data.txt")
if err != nil {
log.Fatalf("无法打开文件：%v", err)
}
defer f.Close()
for cont := true; cont; cont = rows.NextResultSet() {
for rows.Next() {
err := rows.Scan(§ion_id, &modified_by)
if err != nil {
fmt.Println(err)
}
fmt.Println(section_id, modified_by)
n, err := f.WriteString(fmt.Sprintf("%s 修改了 %d", modified_by, section_id))
if err != nil {
log.Fatalf("无法写入文件：%v", err)
}
log.Printf("写入了 %d 字节\n", n)
}
}
首先打开一个文件，并检查是否有错误，然后在循环中再次将每一行写入文件，并在其中进行错误检查。更多示例请参见这里。
英文:
Replace the loop with
f, err := os.Create("data.txt")
if err != nil {
log.Fatalf("could not open file: %v", err)
}
defer f.Close()
for cont := true; cont; cont = rows.NextResultSet() {
for rows.Next() {
err := rows.Scan(&section_id, &modified_by)
if err != nil {
fmt.Println(err)
}
fmt.Println(section_id, modified_by)
n, err := f.WriteString(fmt.Sprintf("%s modified %d", modified_by, section_id))
if err != nil {
log.Fatalf("could not write to file: %v", err)
}
log.Printf("Wrote %d bytes\n", n)
}
}
You first open a file, check for errors and then in the loop write every row to the file again with error checks in between. See here for more examples.
答案2
得分: 0
你可以使用json.MarshalIndent将数据保存为格式化的json文件。
package main
import (
"encoding/json"
"fmt"
"io/ioutil"
)
func ToJsonFile(path string, v interface{}) {
bytes, _ := json.MarshalIndent(v, "", " ")
if err := ioutil.WriteFile(path, bytes, 0644); err != nil {
fmt.Println(err)
panic(err)
}
fmt.Println("已将数据保存为json文件，路径为：" + path)
}
type Enrollment struct {
SectionId string `json:"section_id"`
ModifiedBy string `json:"modified_by"`
}
func PersistData() error {
// 在这里实现数据库操作...
// 用于存放数据的数组
var data []*Enrollment
rows, err := db.Query("select section_id, modified_by from enrollment where rownum < 5")
if err != nil {
fmt.Println("运行查询时出错")
fmt.Println(err)
return err
}
defer rows.Close()
for cont := true; cont; cont = rows.NextResultSet() {
for rows.Next() {
document := &Enrollment{}
err := rows.Scan(&document.SectionId, &document.ModifiedBy)
if err != nil {
fmt.Println(err)
return err
}
data = append(data, document)
fmt.Println(document.SectionId, document.ModifiedBy)
}
}
// 将数据持久化为json文件
ToJsonFile("DATA.json", data)
return nil
}
以上是要翻译的内容。
英文:
You can save your data as a beautified json file using json.MarshalIndent.
package main
import (
"encoding/json"
"fmt"
"io/ioutil"
)
func ToJsonFile(path string, v interface{}) {
bytes, _ := json.MarshalIndent(v, "", " ")
if err := ioutil.WriteFile(path, bytes, 0644); err != nil {
fmt.Println(err)
panic(err)
}
fmt.Println("Saved the data as json file at " + path)
}
type Enrollment struct {
SectionId string `json:"section_id"`
ModifiedBy string `json:"modified_by"`
}
func PersistData() error {
// implement db here ...
// array to put data together
var data []*Enrollment
rows, err := db.Query("select section_id, modified_by from enrollment where rownum < 5")
if err != nil {
fmt.Println("Error running query")
fmt.Println(err)
return err
}
defer rows.Close()
for cont := true; cont; cont = rows.NextResultSet() {
for rows.Next() {
document := &Enrollment{}
err := rows.Scan(&document.SectionId, &document.ModifiedBy)
if err != nil {
fmt.Println(err)
return err
}
data = append(data, document)
fmt.Println(document.SectionId, document.ModifiedBy)
}
}
// persist data to a json file
ToJsonFile("DATA.json", data)
return nil
}
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