繼Golang學習系列第三天https://www.cnblogs.com/dongguangming/p/13311198.html：數組、切片、Map、結構體、指針、函數、接口類型、channel通道，今天開始學習golang操作數據庫，以PostgreSQL為例。
0. 安裝PostgreSQL 數據庫
可以參考PostgreSQL官網https://www.postgresql.org/download/linux/redhat/安裝該數據庫
特別需要說明的是，安裝完成后，自動建立了一個名為postgres的用戶，默認密碼為空；同時也自動創建了一個名字叫postgres的數據庫。
0.1、修改默認生成的數據庫用戶postgres的密碼。
把密碼設置為12345678.
0.2 創建示例數據庫
測試數據庫名可以自取，
然后建一張測試表讓golang使用
CREATE TABLE users ( id serial PRIMARY KEY, email VARCHAR (355) UNIQUE NOT NULL, password VARCHAR (50) NOT NULL ); insert into users(id,email,password) values(1,'1056764180@qq,com','12345678'); insert into users(id,email,password) values(2,'10567@qq,com','1234567890'); insert into users(id,email,password) values(3,'10567567@qq,com','12345678908'); 0.3 開啟遠程訪問
由於數據庫和應用程序不在同一機器上，故數據庫要開啟遠程訪問功能
修改配置文件，即
vim /var/lib/pgsql/12/data/postgresql.conf找到listen_adderess配置項設為*
繼續修改另一配置文件，即
vim /var/lib/pgsql/12/data/pg_hba.conf在# IPv4 local connections:處追加客戶端的連接信息
重啟postgresql服務
systemctl restart postgresql-12最后客戶端測試連接
1. golang操作數據庫
連接數據庫會使用第三方驅動包，由於牆的緣故，可以先設置一下代理
go env -w GO111MODULE=on go env -w GOPROXY=https://mirrors.aliyun.com/goproxy/,direct就以基本的增刪改查數據，記錄如何使用go操作數據庫
1. 1 Select查詢數據
新建postgres.go項目，鍵入以下測試連接數據庫的代碼
package main import ( "database/sql" "fmt" "log" _ "github.com/lib/pq" //_ "github.com/bmizerany/pq" ) const ( // TODO fill this in directly or through environment variable // Build a DSN e.g. postgres://username:password@url.com:5432/dbName DB_DSN = "postgres://postgres:12345678@192.168.8.200:5432/douyin?sslmode=disable" ) type User struct { ID int Email string Password string } func main() { // Create DB pool //db, err := sql.Open("postgres", "host=192.168.8.200 port=5432 user=postgres password=12345678 dbname=douyin sslmode=disable") db, err := sql.Open("postgres",DB_DSN) if err != nil { log.Fatal("Failed to open a DB connection: ", err) } defer db.Close() // Create an empty user and make the sql query (using $1 for the parameter) var myUser User userSql := "SELECT id, email, password FROM users WHERE id = $1" err = db.QueryRow(userSql, 1).Scan(&myUser.ID, &myUser.Email, &myUser.Password) if err != nil { log.Fatal("Failed to execute query: ", err) } fmt.Printf("你好 郵箱：%s, 密碼：%s, 歡迎回來!\n", myUser.Email, myUser.Password) } 然后創建一個模塊依賴文件
go mod init pluginModel安裝具體的依賴包
go get github.com/lib/pq
最后運行測試代碼
[root@master goworkspace]# go run postgres.go從數據庫查詢id等於1的記錄，如圖
和數據庫里的數據是對應的
1.2 增加數據
接上1.1示例代碼，稍作更改即可，文件命名為postgres-create.go
package main
import (
"database/sql"
"fmt"
"log"
_ "github.com/lib/pq"
//_ "github.com/bmizerany/pq"
)
const (
// TODO fill this in directly or through environment variable
// Build a DSN e.g. postgres://username:password@url.com:5432/dbName
DB_DSN = "postgres://postgres:12345678@192.168.8.200:5432/douyin?sslmode=disable"
)
type User struct {
ID int
Email string
Password string
}
func main() {
// Create DB pool
//db, err := sql.Open("postgres", "host=192.168.8.200 port=5432 user=postgres
password=12345678 dbname=douyin sslmode=disable")
db, err := sql.Open("postgres",DB_DSN)
if err != nil {
log.Fatal("Failed to open a DB connection: ", err)
}
defer db.Close()
//創建一個用戶，預要插入到數據庫里
var user User = User{ID:4,Email:"110@qq.com",Password:"1234567890"}
//執行插入操作
_, err = db.Exec("INSERT INTO users (id,email,password) VALUES($1,$2,$3)",
user.ID,user.Email,user.Password)
if err != nil {
log.Fatal(err)
}
//打印日志
log.Printf("create ok!!!")
//測試數據是否插入成功，執行具體的查詢語句
var myUser User
userSql := "SELECT id, email, password FROM users WHERE id = $1"
//設置查詢參數為4，即創建數據時的ID值
err = db.QueryRow(userSql, 4).Scan(&myUser.ID, &myUser.Email,
&myUser.Password)
if err != nil {
log.Fatal("Failed to execute query: ", err)
}
//輸出查詢結果
fmt.Printf("hello email: %s, password: %s, welcome back!\n",
myUser.Email,myUser.Password)
}
執行程序代碼，輸出結果
1.3 update修改數據
接上1.2示例代碼，稍作更改即可，文件命名為postgres-update.go
package main
import (
"database/sql"
"fmt"
"log"
_ "github.com/lib/pq"
//_ "github.com/bmizerany/pq"
)
const (
// TODO fill this in directly or through environment variable
// Build a DSN e.g. postgres://username:password@url.com:5432/dbName
DB_DSN = "postgres://postgres:12345678@192.168.8.200:5432/douyin?sslmode=disable"
)
type User struct {
ID int
Email string
Password string
}
func main() {
// Create DB pool
//db, err := sql.Open("postgres", "host=192.168.8.200 port=5432 user=postgres
password=12345678 dbname=douyin sslmode=disable")
db, err := sql.Open("postgres",DB_DSN)
if err != nil {
log.Fatal("Failed to open a DB connection: ", err)
}
defer db.Close()
//創建一個用戶，預要通過主鍵更改到數據庫里
var user User = User{ID:4,Email:"dong@qq.com",Password:"abcdedf120"}
//執行更改操作
_, err = db.Exec("UPDATE users SET email=$1, password=$2 where id=$3", user.Email,user.Password,user.ID)
if err != nil {
log.Fatal(err)
}
//打印日志
log.Printf("update ok!!!")
//測試數據是否更改成功，執行具體的查詢語句
var myUser User
userSql := "SELECT id, email, password FROM users WHERE id = $1"
//設置查詢參數為4，即要更改數據的ID值
err = db.QueryRow(userSql, 4).Scan(&myUser.ID, &myUser.Email,
&myUser.Password)
if err != nil {
log.Fatal("Failed to execute query: ", err)
}
//輸出查詢結果
fmt.Printf("hello email: %s, password: %s, welcome back!\n",
myUser.Email,myUser.Password)
}
執行程序代碼，輸出結果
1.4 delete刪除數據記錄
接上1.3示例代碼，稍作更改即可，文件命名為postgres-delete.go
package main
import (
"database/sql"
"fmt"
"log"
_ "github.com/lib/pq"
//_ "github.com/bmizerany/pq"
)
const (
// TODO fill this in directly or through environment variable
// Build a DSN e.g. postgres://username:password@url.com:5432/dbName
DB_DSN = "postgres://postgres:12345678@192.168.8.200:5432/douyin?sslmode=disable"
)
type User struct {
ID int
Email string
Password string
}
func main() {
// Create DB pool
//db, err := sql.Open("postgres", "host=192.168.8.200 port=5432 user=postgres
password=12345678 dbname=douyin sslmode=disable")
db, err := sql.Open("postgres",DB_DSN)
if err != nil {
log.Fatal("Failed to open a DB connection: ", err)
}
defer db.Close()
//執行更改操作
_, err = db.Exec("DELETE FROM users where id=$1", 4)
if err != nil {
log.Fatal(err)
}
//打印日志
log.Printf("delete ok!!!")
//測試數據是否更改成功，執行具體的查詢語句
var myUser User
userSql := "SELECT id, email, password FROM users WHERE id = $1"
//設置查詢參數為4，即要更改數據的ID值
err = db.QueryRow(userSql, 4).Scan(&myUser.ID, &myUser.Email,
&myUser.Password)
if err != nil {
log.Fatal("Failed to execute query: ", err)
}
//輸出查詢結果
fmt.Printf("hello email: %s, password: %s, welcome back!\n",
myUser.Email,myUser.Password)
}
執行以上程序代碼，執行輸出結果
至此到這里關於golang操作數據庫postgresql就告一段落了，收工。
代碼已上傳到github：https://github.com/dongguangming/golang-learn/tree/master/go-postgresql
注：由於我沒有用可視化編程工具，是用vi編寫的go代碼，請你們自行排版其結構。
參考：
-
Postgresql 密碼設置 http://www.mamicode.com/info-detail-1977540.html
-
golang連接postgresql數據庫 https://msd.misuland.com/pd/3181438578597038522
-
cannot find module providing package github.com/xxx: working directory is not part of a module https://www.sunzhongwei.com/cannot-find-module-providing-package-githubcomxxx-working-directory-is-not-part-of-a-module
-
SSL is not enabled on the server https://stackoverflow.com/questions/21959148/ssl-is-not-enabled-on-the-server
-
Resolve "FATAL:no pg_hba.conf entry for host" Error when you Connect from PGAdmin4 https://www.cisco.com/c/en/us/support/docs/cloud-systems-management/cloudcenter/212585-resolve-fatal-no-pg-hba-conf-entry-for.html
-
Connect to PostgreSQL and Run a Query https://golangcode.com/postgresql-connect-and-query/
-
golang postgresql CRUD https://www.cnblogs.com/ibgo/p/6010245.html
-