R语言：MySQL, RMySQL on Mac

一些关于mysql在terminal上的指令：
1 .

/mysql -u root -p //进入mysql 数据库

2.

//修改root密码
$ mysql -u root
mysql> use mysql;
mysql> update user set password=PASSWORD("NEWPASSWORD") where User='root';
mysql> flush privileges;
mysql> quit

3. 在MySQL中建库建表

~ mysql -uroot -p
mysql> create database rmysql;
Query OK, 1 row affected (0.00 sec)

mysql> grant all on rmysql.* to rmysql@'%' identified by 'rmysql';
Query OK, 0 rows affected (0.00 sec)

mysql> grant all on rmysql.* to rmysql@localhost identified by 'rmysql';
Query OK, 0 rows affected (0.00 sec)

mysql> use rmysql
Database changed

mysql> CREATE TABLE t_user(
    -> id INT PRIMARY KEY AUTO_INCREMENT,
    -> user varchar(12) NOT NULL UNIQUE
    -> )ENGINE=INNODB DEFAULT CHARSET=utf8;
Query OK, 0 rows affected (0.07 sec)

mysql> INSERT INTO t_user(user) values('A1'),('AB'),('fens.me');
Query OK, 3 rows affected (0.04 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM t_user;

4. 通过R程序，读MySQL数据库数据

//Database Operation
library(RMySQL)
// 建立本地连接
conn <- dbConnect(MySQL(), dbname = "rmysql", username="rmysql", password="rmysql")
// 建立远程连接
conn <- dbConnect(MySQL(), dbname = "rmysql", username="rmysql", password="rmysql",host="192.168.1.201",port=3306)
// 查看数据库的表
dbListTables(conn)
// 查看表的字段
dbListFields(conn, "t_user")
// 查询MySQL信息
summary(MySQL(), verbose = TRUE)
// MySQL连接实例信息
summary(conn, verbose = TRUE)
// MySQL连接信息
dbListConnections(MySQL())

//##########################################
//           RMySQL数据库操作                                           #
//##########################################
// 数据框
t_demo <- dataFrame
// 覆盖原表数据
dbWriteTable(conn, "test", t_demo, overwrite=TRUE)
// 建立新表格
dbWriteTable(conn, "test", t_demo)
// 插入新数据
dbWriteTable(conn, "world_box_office", t_demo, append=TRUE)
# 查看表格
dbReadTable(conn,"test")
// 覆盖原表数据
> dbWriteTable(conn, "t_demo", t_demo, overwrite=TRUE)
// 数据库询问
d0 = dbGetQuery(conn, "SELECT * FROM test")
//执行SQL脚本查询，并分页
rs <- dbSendQuery(conn, "SELECT * FROM test")
d1 <- fetch(rs)
rs <- dbSendQuery(conn, "SELECT * FROM test where Domestic>500")
d1 <- fetch(rs)
rs <- dbSendQuery(conn, "SELECT * FROM test ORDER BY World DESC")
d1 <- fetch(rs)
qu <- dbSendQuery(conn, "show tables")
d2 <- fetch(qu)
// 删除表
if(dbExistsTable(conn,'world_box_office')){
  dbRemoveTable(conn, "world_box_office")
}
// 不插入row.names字段
dbWriteTable(conn, "test", d1,row.names=FALSE,overwrite=TRUE)
// 取消连接，结束数据库
dbDisconnect(conn)

5. RMySQL案例实践
系统需求描述：Linux MySQL，Win7的R环境，远程连接

1. 通过SQL新建表t_blog，主键索引，唯一键索引
2. 用RMySQL插入数据，包括中文字段
3. 再用RMySQL取出数据
1). 通过SQL新建表t_blog，主键索引，唯一键索引
建表语句


CREATE TABLE t_blog(
id INT PRIMARY KEY AUTO_INCREMENT,
title varchar(12) NOT NULL UNIQUE,
author varchar(12) NOT NULL,
length int NOT NULL,
create_date timestamp NOT NULL DEFAULT now()
)ENGINE=INNODB DEFAULT CHARSET=UTF8;

mysql> desc t_blog;
+-------------+-------------+------+-----+-------------------+----------------+
| Field       | Type        | Null | Key | Default           | Extra          |
+-------------+-------------+------+-----+-------------------+----------------+
| id          | int(11)     | NO   | PRI | NULL              | auto_increment |
| title       | varchar(12) | NO   | UNI | NULL              |                |
| author      | varchar(12) | NO   |     | NULL              |                |
| length      | int(11)     | NO   |     | NULL              |                |
| create_date | timestamp   | NO   |     | CURRENT_TIMESTAMP |                |
+-------------+-------------+------+-----+-------------------+----------------+
5 rows in set (0.00 sec)

mysql> show indexes from t_blog;
+--------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table  | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+--------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| t_blog |          0 | PRIMARY  |            1 | id          | A         |           3 |     NULL | NULL   |      | BTREE      |         |               |
| t_blog |          0 | title    |            1 | title       | A         |           3 |     NULL | NULL   |      | BTREE      |         |               |
+--------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
2 rows in set (0.00 sec)


INSERT INTO t_blog(title,author,length) values('你好，第一篇','Conan',20),('RMySQL数据库编程','Conan',99),('R的极客理想系列文章','Conan',15);

mysql> select * from t_blog;
+----+------------------------------+--------+--------+---------------------+
| id | title                        | author | length | create_date         |
+----+------------------------------+--------+--------+---------------------+
|  1 | 你好，第一篇                 | Conan  |     20 | 2013-08-15 00:13:13 |
|  2 | RMySQL数据库编程             | Conan  |     99 | 2013-08-15 00:13:13 |
|  3 | R的极客理想系列文章          | Conan  |     15 | 2013-08-15 00:13:13 |
+----+------------------------------+--------+--------+---------------------+
3 rows in set (0.00 sec)
2). 用RMySQL插入数据，包括中文字段，再取出数据


> library(RMySQL)
> conn <- dbConnect(MySQL(), dbname = "rmysql", username="rmysql", password="rmysql",host="192.168.1.201",port=3306)
>
> dbSendQuery(conn,'SET NAMES gbk')

> dbSendQuery(conn,"INSERT INTO t_blog(title,author,length) values('R插入的新文章','Conan',50)");

>
> query<-dbSendQuery(conn, "SELECT * FROM t_blog")
Warning message:
In mysqlExecStatement(conn, statement, ...) :
  RS-DBI driver warning: (unrecognized MySQL field type 7 in column 4 imported as character)
> data <- fetch(query, n = -1)
> mysqlCloseResult(query)
[1] TRUE
> print(data)
  id               title author length         create_date
1  1        你好，第一篇  Conan     20 2013-08-15 00:13:13
2  2    RMySQL数据库编程  Conan     99 2013-08-15 00:13:13
3  3 R的极客理想系列文章  Conan     15 2013-08-15 00:13:13
4  4       R插入的新文章  Conan     50 2013-08-15 00:29:45
>
> dbDisconnect(conn)
[1] TRUE
特别提示，不能用dbWriteTable函数！！

我们已经完成，掌握了RMySQL的各种使用技巧，希望大家理解原理后，能少犯错误，提高工作效率！

参考: R语言如何连接MySQL的攻略，摘录自粉丝日志
http://blog.fens.me/r-mysql-rmysql/