translate_sql function

Translate an expression to SQL

dbplyr translates commonly used base functions including logical (!, &, |), arithmetic (^), and comparison (!=) operators, as well as common summary (mean(), var()), and transformation (log()) functions. All other functions will be preserved as is. R's infix functions (e.g. %like%) will be converted to their SQL equivalents (e.g. LIKE).

Learn more in vignette("translation-function").

translate_sql(
  ...,
  con,
  vars_group = NULL,
  vars_order = NULL,
  vars_frame = NULL,
  window = TRUE
)

translate_sql_(
  dots,
  con,
  vars_group = NULL,
  vars_order = NULL,
  vars_frame = NULL,
  window = TRUE,
  context = list()
)

Arguments

• ..., dots: Expressions to translate. translate_sql()

  automatically quotes them for you. translate_sql_() expects a list of already quoted objects.

• con: An optional database connection to control the details of the translation. The default, NULL, generates ANSI SQL.

• vars_group, vars_order, vars_frame: Parameters used in the OVER

  expression of windowed functions.

• window: Use FALSE to suppress generation of the OVER

  statement used for window functions. This is necessary when generating SQL for a grouped summary.

• context: Use to carry information for special translation cases. For example, MS SQL needs a different conversion for is.na() in WHERE vs. SELECT clauses. Expects a list.

Examples

con <- simulate_dbi()

# Regular maths is translated in a very straightforward way
translate_sql(x + 1, con = con)
translate_sql(sin(x) + tan(y), con = con)

# Note that all variable names are escaped
translate_sql(like == "x", con = con)
# In ANSI SQL: "" quotes variable _names_, '' quotes strings

# Logical operators are converted to their sql equivalents
translate_sql(x < 5 & !(y >= 5), con = con)
# xor() doesn't have a direct SQL equivalent
translate_sql(xor(x, y), con = con)

# If is translated into case when
translate_sql(if (x > 5) "big" else "small", con = con)

# Infix functions are passed onto SQL with % removed
translate_sql(first %like% "Had%", con = con)
translate_sql(first %is% NA, con = con)
translate_sql(first %in% c("John", "Roger", "Robert"), con = con)

# And be careful if you really want integers
translate_sql(x == 1, con = con)
translate_sql(x == 1L, con = con)

# If you have an already quoted object, use translate_sql_:
x <- quote(y + 1 / sin(t))
translate_sql_(list(x), con = simulate_dbi())

# Windowed translation --------------------------------------------
# Known window functions automatically get OVER()
translate_sql(mpg > mean(mpg), con = con)

# Suppress this with window = FALSE
translate_sql(mpg > mean(mpg), window = FALSE, con = con)

# vars_group controls partition:
translate_sql(mpg > mean(mpg), vars_group = "cyl", con = con)

# and vars_order controls ordering for those functions that need it
translate_sql(cumsum(mpg), con = con)
translate_sql(cumsum(mpg), vars_order = "mpg", con = con)