R如何选择我连接的数据库？

# 安装并加载RMySQL包
install.packages("RMySQL")
library(RMySQL)

# 创建数据库连接
con <- dbConnect(MySQL(),
                 host = "localhost",
                 port = 3306,
                 user = "your_username",
                 password = "your_password",
                 dbname = "your_database")

# 执行查询
result <- dbGetQuery(con, "SELECT * FROM your_table")
print(result)

# 关闭连接
dbDisconnect(con)

# 安装并加载RPostgreSQL包
install.packages("RPostgreSQL")
library(RPostgreSQL)

# 创建数据库连接
con <- dbConnect(PostgreSQL(),
                 host = "localhost",
                 port = 5432,
                 user = "your_username",
                 password = "your_password",
                 dbname = "your_database")

# 执行查询
result <- dbGetQuery(con, "SELECT * FROM your_table")
print(result)

# 关闭连接
dbDisconnect(con)

# 安装并加载mongolite包
install.packages("mongolite")
library(mongolite)

# 创建数据库连接
con <- mongo(collection = "your_collection",
             db = "your_database",
             url = "mongodb://localhost:27017")

# 查询数据
result <- con$find({})
print(result)

# 关闭连接
con$disconnect()