Foreign key column names

dm_get_fk() returns the names of the columns marked as foreign key of table table with respect to table ref_table within a dm object. If no foreign key is set between the tables, an empty character vector is returned.

dm_get_fk(dm, table, ref_table)

Arguments

dm	A dm object.
table	A table in the dm.
ref_table	The table that is referenced from table.

Value

A list of character vectors with the column name(s) of table, pointing to the primary key of ref_table.

Compound keys

Currently, keys consisting of more than one column are not supported. This feature is planned for dm 0.2.0. Therefore the function may return vectors of length greater than one in the future.

See also

Other foreign key functions: dm_add_fk(), dm_enum_fk_candidates(), dm_get_all_fks(), dm_has_fk()

Examples

dm_nycflights13() %>%
  dm_get_fk(flights, airports)
#> <list_of<character>[1]>
#> [[1]]
#> [1] "origin"
#> 
dm_nycflights13(cycle = TRUE) %>%
  dm_get_fk(flights, airports)
#> <list_of<character>[2]>
#> [[1]]
#> [1] "origin"
#> 
#> [[2]]
#> [1] "dest"
#>