R语言使用RClickhouse连接及读写Clickhouse数据库

服务器安装RClickhouse

用R语言做数据分析时，常常需要从多种数据源取数据，其中数据库是非常常见的数据源。RClickhouse包，可以在R语言中对Clickhouse数据库进行增删改查的操作。

安装：

install.packages(“RClickhouse”)

查看一下：

packageVersion("RClickhouse")
> packageVersion("RClickhouse")
[1] ‘0.5.2’

创建DBI Connection:

con <- DBI::dbConnect(RClickhouse::clickhouse(), host="192.168.8.145",db ="test")

注意：请注意，{RClickhouse}不使用HTTP接口与Clickhouse通信。因此，您可以使用本机接口端口（默认为9000）而不是HTTP接口（8123）。

将数据写入数据库:

DBI::dbWriteTable(con, "mtcars", mtcars)
DBI::dbListTables(con)
DBI::dbListFields(con, "mtcars")

使用dplyr查询数据库：

tbl(con, "mtcars") %>% group_by(cyl) %>%summarise(smpg=sum(mpg))

tbl(con, "mtcars") %>% filter(cyl == 8, vs == 0) %>% group_by(am) %>% summarise(mean(qsec))
# Close the connection
DBI::dbDisconnect(con)

使用带有DBI的SQL样式命令查询数据库：:dbGetQuery:

DBI::dbGetQuery(con, "SELECT vs ,COUNT(*) AS 'number of cases',AVG(qsec) AS 'average qsec'FROM mtcars GROUP BY vs")

# Save results of querying:

DBI::dbGetQuery(con, "SELECT (*) FROM mtcars WHERE am = 1")

# Or save the whole set of data (only useful for smaller datasets, for better performance and for larger datasets always use remote servers):

mtcars <- dbReadTable(con, mtcars)

# Close the connection
dbDisconnect(con)

使用ClickHouse函数查询数据库

# Get the names of all the avaliable databases
DBI::dbGetQuery(con, "SHOW DATABASES")

# 查看表
DBI::dbGetQuery(con, "SHOW TABLES")

# Get information about the variable names and types
DBI::dbGetQuery(con, "DESCRIBE TABLE mtcars")

# Compact CASE - WHEN - THEN conditionals
DBI::dbGetQuery(con, "SELECT multiIf(am='1', 'automatic', 'manual') AS 'transmission',multiIf(vs='1', 'straight', 'V-shaped') AS 'engine'FROM mtcars")

# 写入数据,跟Rmysql 语法差不多
diagram<-data.frame(id=4:5,name=c("周璐老师","宋雪老师"))

DBI::dbWriteTable(conn,"test01",diagram,append=T,row.names=F)


# Close the connection
dbDisconnect(con)