golang基础-Postgresql使用、Go中使用PostgreSQL（github.com/lib/pq学习）
文章目录
- postgresql介绍
- postgresql安装使用(mac下)
- Go中使用PostgreSQL（github.com/lib/pq学习）
- 连接postgres
- 查询postgres
- 单条查询QueryRow
- 插入
- 修改
- 删除
postgresql介绍
官网
https://www.postgresql.org/
PostgreSQL is a powerful, open source object-relational database system.
PostgreSQL是一个功能强大的开源对象关系数据库管理系统(ORDBMS)。 用于安全地存储数据; 支持最佳做法，并允许在处理请求时检索它们。
特点
PostgreSQL可在所有主要操作系统(即Linux，UNIX(AIX，BSD，HP-UX，SGI IRIX，Mac OS X，Solaris，Tru64)和Windows等)上运行
PostgreSQL支持文本，图像，声音和视频，并包括用于C/C++，Java，Perl，Python，Ruby，Tcl和开放数据库连接(ODBC)的编程接口
PostgreSQL支持SQL的许多功能，例如复杂SQL查询，SQL子选择，外键，触发器，视图，事务，多进程并发控制(MVCC)，流式复制(9.0)，热备(9.0))
在PostgreSQL中，表可以设置为从“父”表继承其特征
可以安装多个扩展以向PostgreSQL添加附加功能
postgresql安装使用(mac下)
在Mac系统上通过通过brew into [email protected] 安装数据库进行安装即可
配置环境变量
echo 'export PATH="/usr/local/opt/[email protected]/bin:$PATH"' >> ~/.bash_profile
启动
pg_ctl -D /usr/local/var/postgresql\@9.6/ -l logfile start
server starting
关闭
pg_ctl -D /usr/local/var/postgresql\@9.6/ stop -s -m fast
下面先罗列一些简单的postgresql命令
创建用户
CREATE USER wyfzhiliao with password 'wyf';
创建数据库
CREATE DATABASE go OWNER wyfzhiliao;
授权
GRANT ALL PRIVILEGES ON DATABASE zldd_api TO wyfzhiliao;
系统用户登入
psql postgres
系统用户直接登入访问某个库
psql -U wyfzhiliao -d zldd_user -h 127.0.0.1
链接数据库
zldd_api=> \c zldd_user
创建表
CREATE TABLE u_order(
id varchar(40) PRIMARY KEY NOT NULL,
app_id varchar(40),
mch_id varchar(40),
nonce_str varchar(40),
sign varchar(40),
sign_type varchar(40),
body varchar(130),
out_trade_no varchar(40),
total_fee int,
fee_type varchar(10) default 'CNY' ,
spbill_create_ip varchar(20),
time_start timestamp with time zone,
time_expire timestamp with time zone,
trade_type varchar(20),
wechat_open_id varchar(130),
wechat_union_id varchar(130),
wechat_pay_key varchar(40),
user_id varchar(40),
platform varchar(20),
pay_courses text[],
pay_status int
);
类型如下：
go_api=# \d u_order;
Table "public.u_order"
Column | Type | Modifiers
------------------+--------------------------+----------------------------------
id | character varying(40) | not null
app_id | character varying(40) |
mch_id | character varying(40) |
nonce_str | character varying(40) |
sign | character varying(40) |
sign_type | character varying(40) |
body | character varying(130) |
out_trade_no | character varying(40) |
total_fee | integer |
fee_type | character varying(10) | default 'CNY'::character varying
spbill_create_ip | character varying(20) |
time_start | timestamp with time zone |
time_expire | timestamp with time zone |
trade_type | character varying(20) |
wechat_open_id | character varying(130) |
wechat_union_id | character varying(130) |
wechat_pay_key | character varying(40) |
user_id | character varying(40) |
platform | character varying(20) |
pay_courses | text[] |
pay_status | integer |
Indexes:
"u_order_pkey" PRIMARY KEY, btree (id)
go_api=# \d go
列举出数据库中的表
zldd_user=> \d
列举创建的数据库
zldd_user=> \l
退出
postgres-# \q
创建表
CREATE TABLE products (
product_no integer,
name text,
price numeric
);
删除表
drop table products;
查询表
go=> select * from products;
product_no | name | price
------------+------+-------
(0 rows)
插入表
go=> INSERT INTO products VALUES (1, 'Cheese', 9.99);
INSERT 0 1
go=> select * from products;
product_no | name | price
------------+--------+-------
1 | Cheese | 9.99
(1 row)
go=>
Go中使用PostgreSQL（github.com/lib/pq学习）
安装
go get -u github.com/lib/pq
参考资料
https://godoc.org/github.com/lib/pq
连接postgres
package main
import (
"database/sql"
"fmt"
_ "github.com/lib/pq"
)
const (
host = "localhost"
port = 5432
user = "wyfzhiliao"
password = "wyfzhiliao"
dbname = "go"
)
func main() {
psqlInfo := fmt.Sprintf("host=%s port=%d user=%s "+
"password=%s dbname=%s sslmode=disable",
host, port, user, password, dbname)
db, err := sql.Open("postgres", psqlInfo)
if err != nil {
panic(err)
}
defer db.Close()
err = db.Ping()
if err != nil {
panic(err)
}
fmt.Println("Successfully connected!")
}
sql.Open的第一个参数是driver名称，第二个参数是driver连接数据库的信息。DB不是连接，并且只有当需要使用时才会创建连接，如果想立即验证连接，需要用Ping()方法，如下：
You can also connect to a database using a URL. For example:
connStr := "postgres://pqgotest:password@localhost/pqgotest?sslmode=verify-full"
db, err := sql.Open("postgres", connStr)
输出如下：
另外列出出来可以使用的参数：
* dbname - The name of the database to connect to
* user - The user to sign in as
* password - The user's password
* host - The host to connect to. Values that start with / are for unix
domain sockets. (default is localhost)
* port - The port to bind to. (default is 5432)
* sslmode - Whether or not to use SSL (default is require, this is not
the default for libpq)
* fallback_application_name - An application_name to fall back to if one isn't provided.
* connect_timeout - Maximum wait for connection, in seconds. Zero or
not specified means wait indefinitely.
* sslcert - Cert file location. The file must contain PEM encoded data.
* sslkey - Key file location. The file must contain PEM encoded data.
* sslrootcert - The location of the root certificate file. The file
must contain PEM encoded data.
查询postgres
现在我的postgresql数据库中有如下一条记录
go=> select * from products where name='Proto';
product_no | name | price
------------+-------+-------
2 | Proto | 9.99
(1 row)
接下来我们将它查询出来，看如下代码
package main
import (
"database/sql"
"fmt"
_ "github.com/lib/pq"
)
const (
host = "localhost"
port = 5432
user = "wyfzhiliao"
password = "wyfzhiliao"
dbname = "go"
)
func connectDB() *sql.DB{
psqlInfo := fmt.Sprintf("host=%s port=%d user=%s "+
"password=%s dbname=%s sslmode=disable",
host, port, user, password, dbname)
db, err := sql.Open("postgres", psqlInfo)
if err != nil {
panic(err)
}
err = db.Ping()
if err != nil {
panic(err)
}
return db
}
func query(db *sql.DB){
var id,name,price string
rows,err:=db.Query(" select * from products where name=$1","Proto")
if err!= nil{
fmt.Println(err)
}
defer rows.Close()
for rows.Next(){
err:= rows.Scan(&id,&name,&price)
if err!= nil{
fmt.Println(err)
}
}
err = rows.Err()
if err!= nil{
fmt.Println(err)
}
fmt.Println(id,name,price)
}
func main() {
db:=connectDB()
query(db)
}
输出结果如下：
2 Proto 9.99
上面代码的过程为：db.Query()表示向数据库发送一个query，defer rows.Close()非常重要（关闭连接），遍历rows使用rows.Next()，把遍历到的数据存入变量使用rows.Scan()，遍历完成后检查error。有几点需要注意：
(1) 检查遍历是否有error
(2) 结果集(rows)未关闭前，底层的连接处于繁忙状态。当遍历读到最后一条记录时，会发生一个内部EOF错误，自动调用rows.Close()，但是如果提前退出循环，rows不会关闭，连接不会回到连接池中，连接也不会关闭。所以手动关闭非常重要。rows.Close()可以多次调用，是无害操作。
单条查询QueryRow
当我们查询单条记录时候，我们可以直接用QueryRow
func query_one(db *sql.DB){
var price string
err := db.QueryRow(" select price from products where name=$1", "Proto").Scan(&price)
if err != nil {
if err == sql.ErrNoRows {
} else {
log.Fatal(err)
}
}
fmt.Println(price)
}
输出结果如下：
9.99
插入
func insertUser(db *sql.DB) {
stmt,err := db.Prepare("insert into products(product_no,name,price) values($1,$2,$3)")
if err != nil {
log.Fatal(err)
}
_,err = stmt.Exec(6,"dump","10.88")
if err != nil {
log.Fatal(err)
}else {
fmt.Println("insert into user_tbl success")
}
}
插入结果如下，我们看到数据库多了一条记录
go=> select * from products;
product_no | name | price
------------+--------+-------
1 | Cheese | 9.99
2 | Proto | 9.99
6 | dump | 10.88
(3 rows)
修改
func UpdateUser(db *sql.DB) {
stmt,err := db.Prepare("UPDATE products set price=$1 WHERE product_no=$2")
if err != nil {
log.Fatal(err)
}
_,err = stmt.Exec("11.88",6)
if err != nil {
log.Fatal(err)
}else {
fmt.Println("udpate user_tbl success")
}
}
更新后的数据库记录
go=> select * from products;
product_no | name | price
------------+--------+-------
1 | Cheese | 9.99
2 | Proto | 9.99
6 | dump | 11.88
(3 rows)
删除
func DeleteUser(db *sql.DB) {
stmt,err := db.Prepare("DELETE FROM products WHERE product_no=$1")
if err != nil {
log.Fatal(err)
}
_,err = stmt.Exec(6)
if err != nil {
log.Fatal(err)
}else {
fmt.Println("delete form user_tbl success")
}
}
删除记录后的数据库数据
go=> select * from products;
product_no | name | price
------------+--------+-------
1 | Cheese | 9.99
2 | Proto | 9.99
(2 rows)
go=>