Q: Is there a 'cleaner' way to concatenate a query string? I am passing a query string to a connection and the result should look like this:
select game_name, month, count(*) as count
  from device_metrics.mtu_events
 where YEAR = '2019' and month between '07' and '09'
 group by game_name, month
 order by game_name asc, month asc

This works fine if I pass the above block as a single string into DBI::dbGetQuery(con, myquery)
But the dates are a variable within a shiny app, so I tried to create a function to generate the query string:
my_query <- function(start_date, end_date) {
        yr <- year(ymd(start_date))
        month_start <- month(ymd(start_date))
        month_end <- month(ymd(end_date))

        query <- paste0(
            "select game_name, month, count(*) as count
   from device_metrics.mtu_events
   where YEAR = ", yr, " and month between ", month_start, " and ", month_end, 
            " group by game_name, month
 order by game_name asc, month asc")

        return(query)
    }

When I call this function and try to query our database with it I get:

An error has been thrown from the AWS Athena client. Athena Error No: 372, HTTP Response Code: 1, Error Message: SYNTAX_ERROR: line 3:15: '=' cannot be applied to varchar, integer

Is there a 'right' way to do this? How can I construct a query string with variables and pass then to DBI::dbGetQuery()

A: Here are two options where we can quote (') the input as a string as month, year functions return numeric values
my_query <- function(start_date, end_date) {
        yr <- year(ymd(start_date))
        month_start <- month(ymd(start_date))
        month_end <- month(ymd(end_date))

        query <- paste0(
            "select game_name, month, count(*) as count
   from device_metrics.mtu_events
   where YEAR = '", yr, "' and month between '", month_start, "' and '", month_end, 
            "' group by game_name, month
 order by game_name asc, month asc")

        return(query)
    }


Using sprintf
my_query <- function(start_date, end_date) {
            yr <- year(ymd(start_date))
            month_start <- month(ymd(start_date))
            month_end <- month(ymd(end_date))

            query <- sprintf("select game_name, month, count(*) as count
       from device_metrics.mtu_events
       where YEAR = '%d'  and month between '%02d' and '%02d' group by game_name, month
     order by game_name asc, month asc", yr, month_start, month_end)

            return(query)
        }


A: We can use fn$ from gsubfn to perform string interpolation.  We will use NULL instead of an actual connection and fn$list instead of fn$dbGetQuery for purposes of reproducibility but you can replace both.  Do not use underscores or dots in names when doing this.
library(gsubfn)

yr <- 2019
monthStart <- '07'
monthEnd <- '09'
con <- NULL

fn$list(con, "select game_name, month, count(*) as count
  from device_metrics.mtu_events
 where YEAR = '$yr' and month between '$monthStart' and '$monthEnd'
 group by game_name, month
 order by game_name asc, month asc")

It could alternately be done in two steps:
query <- fn$c("select game_name, month, count(*) as count
  from device_metrics.mtu_events
 where YEAR = '$yr' and month between '$monthStart' and '$monthEnd'
 group by game_name, month
 order by game_name asc, month asc")
dbGetQuery(con, query)

