Build a query that applies a SQL expression to a set of columns.

sql_expr_set(source, cols, expr)

Arguments

source	incoming rel_op tree or data.frame.
cols	character, columns to operate in. If a named array names are where results are landed, values names of value columns.
expr	character or list of character and names, expression to apply to columns "." stands for column value to use.

Value

rel_op node or data.frame (depending on input).

Examples


# WARNING: example tries to change rquery.rquery_db_executor option to RSQLite and back.
if (requireNamespace("DBI", quietly = TRUE) && requireNamespace("RSQLite", quietly = TRUE)) {
  my_db <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
  RSQLite::initExtension(my_db)
  old_o <- options(list("rquery.rquery_db_executor" = list(db = my_db)))

  d <- rq_copy_to(my_db, 'd',
                   data.frame(AUC = c(NA, 0.5, NA),
                              R2 = c(1.0, 0.9, NA),
                              delta = 3,
                              cat = c("a", NA, "c"),
                              stringsAsFactors = FALSE))

  # example
  op_tree <- d %.>% sql_expr_set(., qc(AUC, R2), ". + 1")
  cat(format(op_tree))
  sql <- to_sql(op_tree, my_db)
  cat(sql)
  print(DBI::dbGetQuery(my_db, sql))

  # ex2 names (but not marked as names)
  op_tree2 <- d %.>% sql_expr_set(., qc(AUC, R2),
     ". + 1 + delta")
  cat(to_sql(op_tree2, my_db))

  # ex3 names (also so marked)
  op_tree3 <- d %.>% sql_expr_set(., qc(AUC, R2),
     list(". + 1 +", as.name("delta")))
  cat(to_sql(op_tree3, my_db))

  # cleanup
  options(old_o)
  DBI::dbDisconnect(my_db)
}
#> mk_td("d", c(
#>   "AUC",
#>   "R2",
#>   "delta",
#>   "cat")) %.>%
#>  sql_node(.,
#>           sql_expr_set(AUC, R2; . + 1))
#> SELECT
#>  `AUC` + 1 AS `AUC`,
#>  `R2` + 1 AS `R2`,
#>  delta AS `delta`,
#>  cat AS `cat`
#> FROM (
#>  SELECT
#>   `AUC`,
#>   `R2`,
#>   `delta`,
#>   `cat`
#>  FROM
#>   `d`
#> ) tsql_98041527705993187917_0000000000
#>   AUC  R2 delta  cat
#> 1  NA 2.0     3    a
#> 2 1.5 1.9     3 <NA>
#> 3  NA  NA     3    c
#> SELECT
#>  `AUC` + 1 + delta AS `AUC`,
#>  `R2` + 1 + delta AS `R2`,
#>  delta AS `delta`,
#>  cat AS `cat`
#> FROM (
#>  SELECT
#>   `AUC`,
#>   `R2`,
#>   `delta`,
#>   `cat`
#>  FROM
#>   `d`
#> ) tsql_29089998058038316191_0000000000
#> SELECT
#>  `AUC` + 1 + `delta` AS `AUC`,
#>  `R2` + 1 + `delta` AS `R2`,
#>  delta AS `delta`,
#>  cat AS `cat`
#> FROM (
#>  SELECT
#>   `AUC`,
#>   `R2`,
#>   `delta`,
#>   `cat`
#>  FROM
#>   `d`
#> ) tsql_74079201325635949115_0000000000

Build a query that applies a SQL expression to a set of columns.

Arguments

Value

See also

Examples