check-cardinalities.md
In dm: Relational Data Models

check_cardinality_...() functions work without `x_select` and `y_select`

Code
  examine_cardinality(data_card_1(), data_card_11())
Output
  [1] "injective mapping (child: 0 or 1 -> parent: 1)"
Code
  examine_cardinality(data_card_1(), data_card_12())
Output
  [1] "surjective mapping (child: 1 to n -> parent: 1)"
Code
  examine_cardinality(data_card_1(), suppress_mssql_message(compute(data_card_1())))
Output
  [1] "bijective mapping (child: 1 -> parent: 1)"
Code
  examine_cardinality(data_card_1(), data_card_11())
Output
  [1] "injective mapping (child: 0 or 1 -> parent: 1)"

check_cardinality_...() API errors

Code
  check_card_api(data_mcard_1(), a, data_mcard_2(), b)
Condition
  Warning:
  The `pk_column` argument of `eval()` is deprecated as of dm 1.0.0.
  i Please use the `x_select` argument instead.
  * Use `y_select` instead of `fk_column`, and `x` and `y` instead of `parent_table` and `child_table`.
  * Using `by_position = TRUE` for compatibility.
Output
  [[1]]
  # A tibble: 3 x 1
        a
    <dbl>
  1     1
  2     2
  3     1

  [[2]]
  # A tibble: 3 x 1
        b
    <dbl>
  1     4
  2     5
  3     6

  [[3]]
  [1] "data_mcard_1()"

  [[4]]
  [1] "data_mcard_2()"

Code
  check_card_api(data_mcard_1(), data_mcard_2(), x_select = a, y_select = c)
Condition
  Error in `check_card_api_impl()`:
  ! `by_position = FALSE` or `by_position = NULL` require column names in `x` to match those in `y`.

check_cardinality_...() functions are checking the cardinality correctly?

Code
  expect_dm_error(check_cardinality_0_n(data_card_1(), data_card_2(), x_select = a,
  y_select = a), class = "not_subset_of")
Output
  # A tibble: 1 x 1
        a
    <dbl>
  1     6
Code
  expect_dm_error(check_cardinality_1_1(data_card_5(), data_card_4(), x_select = a,
  y_select = c(a = c)), class = "not_bijective")
  expect_dm_error(check_cardinality_1_1(data_card_4(), data_card_5(), x_select = c,
  y_select = c(c = a)), class = "not_unique_key")
  expect_dm_error(check_cardinality_1_1(data_card_4(), data_card_1(), x_select = c,
  y_select = c(c = a)), class = "not_unique_key")
  expect_dm_error(check_cardinality_0_1(data_card_1(), data_card_4(), x_select = a,
  y_select = c(a = c)), class = "not_injective")
  expect_dm_error(check_cardinality_0_n(data_card_4(), data_card_1(), x_select = c,
  y_select = c(c = a)), class = "not_unique_key")
  expect_dm_error(check_cardinality_1_1(data_card_4(), data_card_1(), x_select = c,
  y_select = c(c = a)), class = "not_unique_key")
  expect_dm_error(check_cardinality_1_1(data_card_1(), data_card_4(), x_select = a,
  y_select = c(a = c)), class = "not_bijective")

check_cardinality_...() functions are supporting compound keys

Code
  expect_dm_error(check_cardinality_0_n(data_card_1(), data_card_2(), x_select = c(
    a, b), y_select = c(a, b)), class = "not_subset_of")
Output
  # A tibble: 4 x 2
        a b    
    <dbl> <chr>
  1     3 b    
  2     4 c    
  3     5 d    
  4     6 e    
Code
  expect_dm_error(check_cardinality_1_1(data_card_1(), data_card_12(), x_select = c(
    a, b), y_select = c(a, b)), class = "not_bijective")
  expect_dm_error(check_cardinality_1_1(data_card_12(), data_card_1(), x_select = c(
    a, b), y_select = c(a, b)), class = "not_unique_key")
  expect_dm_error(check_cardinality_0_1(data_card_1(), data_card_12(), x_select = c(
    b, a), y_select = c(b, a)), class = "not_injective")