R/select_columns.R
select_columns.Rd
Make a select columns node (not a relational operation).
select_columns(source, columns, env = parent.frame())
source to select from.
list of distinct column names.
environment to look to.
select columns node.
if (requireNamespace("DBI", quietly = TRUE) && requireNamespace("RSQLite", quietly = TRUE)) {
my_db <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
d <- rq_copy_to(my_db, 'd',
data.frame(AUC = 0.6, R2 = 0.2))
optree <- select_columns(d, 'AUC')
cat(format(optree))
sql <- to_sql(optree, my_db)
cat(sql)
print(DBI::dbGetQuery(my_db, sql))
DBI::dbDisconnect(my_db)
}
#> mk_td("d", c(
#> "AUC",
#> "R2")) %.>%
#> select_columns(.,
#> c('AUC'))
#> SELECT
#> `AUC`
#> FROM (
#> SELECT
#> `AUC`
#> FROM
#> `d`
#> ) tsql_65234858906043482779_0000000000
#> AUC
#> 1 0.6