dm (version 0.0.5.9000)

cdm_enum_fk_candidates: Find foreign key candidates in a table

Description

Determine which columns would be good candidates to be used as foreign keys of a table, to reference the primary key column of another table of the dm object.

Usage

cdm_enum_fk_candidates(dm, table, ref_table)
enum_fk_candidates(zoomed_dm, ref_table)

Arguments

dm

A dm object.

table

The table whose columns should be tested for suitability as foreign keys.

ref_table

A table with a primary key.

zoomed_dm

A dm with a zoomed table.

Value

A table that lists which columns of table would be suitable candidates for foreign key columns to reference ref_table, which columns would not be suitable, and the reason why.

Details

cdm_enum_fk_candidates() first checks if ref_table has a primary key set, if not, an error is thrown.

If ref_table does have a primary key, then a join operation will be tried using that key as the by argument of join() to match it to each column of table. Attempting to join incompatible columns triggers an error.

The outcome of the join operation determines the value of the why column in the result:

• an empty value for a column of table that is a suitable foreign key candidate

• the count and percentage of missing matches for a column that is not suitable

• the error message triggered for unsuitable candidates that may include the types of mismatched columns

enum_fk_candidates() works like cdm_enum_fk_candidates() with the zoomed table as table.

See Also

Other foreign key functions: cdm_add_fk(), cdm_get_all_fks(), cdm_get_fk(), cdm_has_fk(), cdm_rm_fk()

Examples

# NOT RUN {
cdm_enum_fk_candidates(cdm_nycflights13(), flights, airports)

# }