Create, modify, and delete columns — mutate.tbl

These are methods for the dplyr mutate() and transmute() generics. They are translated to computed expressions in the SELECT clause of the SQL query.

# S3 method for tbl_lazy
mutate(.data, ...)

Arguments

.data	A lazy data frame backed by a database query.
...	<`data-masking`> Variables, or functions or variables. Use `desc()` to sort a variable in descending order.

Value

Another tbl_lazy. Use show_query() to see the generated query, and use collect() to execute the query and return data to R.

Examples

library(dplyr, warn.conflicts = FALSE)

db <- memdb_frame(x = 1:5, y = 5:1)
db %>%
  mutate(a = (x + y) / 2, b = sqrt(x^2L + y^2L)) %>%
  show_query()
#> <SQL>
#> SELECT `x`, `y`, (`x` + `y`) / 2.0 AS `a`, SQRT(POWER(`x`, 2) + POWER(`y`, 2)) AS `b`
#> FROM `dbplyr_023`

# dbplyr automatically creates subqueries as needed
db %>%
  mutate(x1 = x + 1, x2 = x1 * 2) %>%
  show_query()
#> <SQL>
#> SELECT `x`, `y`, `x1`, `x1` * 2.0 AS `x2`
#> FROM (SELECT `x`, `y`, `x` + 1.0 AS `x1`
#> FROM `dbplyr_023`)