select_columns: Make a select columns node (not a relational operation).

In WinVector/rquery: Relational Query Generator for Data Manipulation at Scale

Make a select columns node (not a relational operation).

Description

Make a select columns node (not a relational operation).

Usage

select_columns(source, columns, env = parent.frame())

Arguments

source	source to select from.
columns	list of distinct column names.
env	environment to look to.

Value

select columns node.

Examples

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)
}

WinVector/rquery documentation built on Aug. 24, 2023, 11:12 a.m.