This tutorial explains how to run sql queries in R with sqldf package.
Install and Load Package
Example 3 : Subset rows
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| Run SQL query in R |
install.packages("sqldf")
library(sqldf)
Create sample data
dt <- data.frame( ID = c('X1','X2','X4','X2','X1','X4','X3','X2','X1','X3'),
Value = c(4,3,1,3,4,6,6,1,8,4))
Example 1 : Select first 3 rows
x = sqldf("select * from dt limit 3")
Example 2 : Handle dot (.) in Column and Table names
Put the names in double quotes
test <- data.frame( x.1 = 1:10 )
sqldf( 'SELECT "x.1" FROM test' )
test.2 = data.frame(x= sample(10))
sqldf( 'SELECT * FROM "test.2"' )
x2 = sqldf("select * from dt where Value >= 4")
Example 4 : Concatenate two data frames
x3 = sqldf("select * from x union all select * from x2")Example 5 : Create a new variable
x4 = sqldf("select *, value*2 as newval from dt ")Example 6 : Merge with another table
dt2 <- data.frame( ID = c('A1','A2','A4','A2','A1','A4','A3','A2','A1','A3'),
ColID = c('Saving',
'Current',
'Loan',
'Current',
'Saving',
'Loan',
'Mortgage',
'Current',
'Saving',
'Mortgage'))
x5 = sqldf("select a.*,b.ColID from dt a left join (select distinct ID, ColID from dt2) bExample 7 : Working with Dates
on a.ID = b.ID")
library(RH2)Example 8 : Cumulative Sum
test1 <- data.frame(sale_date = as.Date(c("2008-08-01", "2031-01-09","1990-01-03")))
as.numeric(test1[[1]])
sqldf("select MAX(sale_date) from test1")
library(RPostgreSQL)Example 9 : Ranking within Group
# Upper case is folded to lower case by default so surround ID with double quotes
x6 = sqldf("select *, sum(Value) over (partition by "ID" order by Value) colsum from dt ")
library(RPostgreSQL)
# Upper case is folded to lower case by default so surround ID with double quotes
x7 = sqldf("select *, rank() over (partition by "ID" order by Value) rank from dt")