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 postgresql@9.6 安装数据库进行安装即可

配置环境变量

echo 'export PATH="/usr/local/opt/postgresql@9.6/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 nullapp_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 varyingspbill_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 mainimport ("database/sql""fmt"_ "github.com/lib/pq"
)const (host     = "localhost"port     = 5432user     = "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 unixdomain 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 notthe 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 ornot 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 filemust 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 mainimport ("database/sql""fmt"_ "github.com/lib/pq"
)const (host     = "localhost"port     = 5432user     = "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 stringrows,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 stringerr := 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 |  9.992 | Proto  |  9.996 | 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 |  9.992 | Proto  |  9.996 | 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 |  9.992 | Proto  |  9.99
(2 rows)go=>