Golang学习系列第四天：操作数据库PostgreSQL
继Golang学习系列第三天：学习数组、切片、Map、结构体、指针、函数、接口类型、channel通道，今天开始学习golang操作数据库，以PostgreSQL为例。
0. 安装PostgreSQL 数据库
可以参考PostgreSQL官网https://www.postgresql.org/download/linux/redhat/安装该数据库
特别需要说明的是，安装完成后，自动建立了一个名为postgres的用户，默认密码为空；同时也自动创建了一个名字叫postgres的数据库。
0.1、修改默认生成的数据库用户postgres的密码。
把密码设置为12345678.
0.2 创建示例数据库
测试数据库名可以自取，
然后建一张测试表让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 开启远程访问
由于数据库和应用程序不在同一机器上，故数据库要开启远程访问功能
修改配置文件，即
vim /var/lib/pgsql/12/data/postgresql.conf找到listen_adderess配置项设为*
继续修改另一配置文件，即
vim /var/lib/pgsql/12/data/pg_hba.conf在# IPv4 local connections:处追加客户端的连接信息
重启postgresql服务
systemctl restart postgresql-12最后客户端测试连接
1. golang操作数据库
连接数据库会使用第三方驱动包，由于墙的缘故，可以先设置一下代理
go env -w GO111MODULE=on
go env -w GOPROXY=https://mirrors.aliyun.com/goproxy/,direct就以基本的增删改查数据，记录如何使用go操作数据库
1. 1 Select查询数据
新建postgres.go项目，键入以下测试连接数据库的代码
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:[email protected]:5432/dbName
DB_DSN = "postgres://postgres:[email protected]: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 邮箱：%s, 密码：%s, 欢迎回来!\n", myUser.Email, myUser.Password)
}
然后创建一个模块依赖文件
go mod init pluginModel安装具体的依赖包
go get github.com/lib/pq
最后运行测试代码
[root@master goworkspace]# go run postgres.go从数据库查询id等于1的记录，如图
和数据库里的数据是对应的
1.2 增加数据
接上1.1示例代码，稍作更改即可，文件命名为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:[email protected]:5432/dbName
DB_DSN = "postgres://postgres:[email protected]: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()
//创建一个用户，预要插入到数据库里
var user User = User{ID:4,Email:"[email protected]",Password:"1234567890"}
//执行插入操作
_, 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!!!")
//测试数据是否插入成功，执行具体的查询语句
var myUser User
userSql := "SELECT id, email, password FROM users WHERE id = $1"
//设置查询参数为4，即创建数据时的ID值
err = db.QueryRow(userSql, 4).Scan(&myUser.ID, &myUser.Email,
&myUser.Password)
if err != nil {
log.Fatal("Failed to execute query: ", err)
}
//输出查询结果
fmt.Printf("hello email: %s, password: %s, welcome back!\n",
myUser.Email,myUser.Password)
}
执行程序代码，输出结果
1.3 update修改数据
接上1.2示例代码，稍作更改即可，文件命名为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:[email protected]:5432/dbName
DB_DSN = "postgres://postgres:[email protected]: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()
//创建一个用户，预要通过主键更改到数据库里
var user User = User{ID:4,Email:"[email protected]",Password:"abcdedf120"}
//执行更改操作
_, 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!!!")
//测试数据是否更改成功，执行具体的查询语句
var myUser User
userSql := "SELECT id, email, password FROM users WHERE id = $1"
//设置查询参数为4，即要更改数据的ID值
err = db.QueryRow(userSql, 4).Scan(&myUser.ID, &myUser.Email,
&myUser.Password)
if err != nil {
log.Fatal("Failed to execute query: ", err)
}
//输出查询结果
fmt.Printf("hello email: %s, password: %s, welcome back!\n",
myUser.Email,myUser.Password)
}
执行程序代码，输出结果
1.4 delete删除数据记录
接上1.3示例代码，稍作更改即可，文件命名为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:[email protected]:5432/dbName
DB_DSN = "postgres://postgres:[email protected]: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()
//执行更改操作
_, err = db.Exec("DELETE FROM users where id=$1", 4)
if err != nil {
log.Fatal(err)
}
//打印日志
log.Printf("delete ok!!!")
//测试数据是否更改成功，执行具体的查询语句
var myUser User
userSql := "SELECT id, email, password FROM users WHERE id = $1"
//设置查询参数为4，即要更改数据的ID值
err = db.QueryRow(userSql, 4).Scan(&myUser.ID, &myUser.Email,
&myUser.Password)
if err != nil {
log.Fatal("Failed to execute query: ", err)
}
//输出查询结果
fmt.Printf("hello email: %s, password: %s, welcome back!\n",
myUser.Email,myUser.Password)
}
执行以上程序代码，执行输出结果
至此到这里关于golang操作数据库postgresql就告一段落了，收工。
代码已上传到github：https://github.com/dongguangming/golang-learn/tree/master/go-postgresql
注：由于我没有用可视化编程工具，是用vi编写的go代码，请你们自行排版其结构。
参考：
-
Postgresql 密码设置 http://www.mamicode.com/info-detail-1977540.html
-
golang连接postgresql数据库 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