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SQL helpers for aggregate functions

Source: R/translate-sql-aggregate.R
sql_translation_agg.Rd

These functions help you create custom aggregate SQL translations when implementing a new backend. They are typically used within sql_translator() to define how R aggregate functions should be translated to SQL.

  • sql_aggregate() creates a SQL aggregate function translator for functions with a single argument and an optional na.rm parameter (e.g., SUM(), AVG()).

  • sql_aggregate_2() creates a SQL aggregate function translator for functions with exactly two arguments (e.g., CORR(), COVAR_SAMP()).

  • sql_aggregate_n() creates a SQL aggregate function translator for functions with any number of arguments and an optional na.rm parameter (e.g., LEAST(), GREATEST()).

  • sql_not_supported() creates a function that throws an informative error when a function is not supported in SQL.

  • sql_check_na_rm() is a helper that you can use in aggregate functions to direct the user towards setting na.rm = TRUE.

Usage

sql_aggregate(f, f_r = f)

sql_aggregate_2(f)

sql_aggregate_n(f, f_r = f)

sql_check_na_rm(na.rm)

sql_not_supported(f)

Arguments

f

The name of the SQL function as a string.

f_r

The name of the R function being translated as a string.

na.rm

Logical indicating whether missing values should be removed. In SQL, missing values are always removed in aggregate functions, so this function will warn if na.rm is not TRUE.

See also

Other SQL translation helpers: sql_translation_scalar, sql_translation_string, sql_translation_window, sql_variant()