ORDINAL 在這個大查詢語法中意味着什么？

Question

嗨，我正在處理此代碼並將重新創建此代碼，但我不知道這一行中序數的含義。

IF(ARRAY_LENGTH(encounter.participant )>0, encounter.participant[ORDINAL(1)].individual.practitionerid, null)

Answer 1

ORDINAL function 是一種用於訪問給定數組中元素的索引。 在您的示例腳本中，它僅表示數組的第一個元素。

如需其他參考，有兩種類型的索引：

• ORDINAL : 用於從一開始的索引
• OFFSET ：用於從零開始的索引

例如：

WITH items AS
  (SELECT ["apples", "bananas", "pears", "grapes"] as list
  UNION ALL
  SELECT ["coffee", "tea", "milk" ] as list
  UNION ALL
  SELECT ["cake", "pie"] as list)

SELECT list, list[OFFSET(1)] as offset_1, list[ORDINAL(1)] as ordinal_1
FROM items;

Output：

+----------------------------------+-----------+-----------+
| list                             | offset_1  | ordinal_1 |
+----------------------------------+-----------+-----------+
| [apples, bananas, pears, grapes] | bananas   | apples    |
| [coffee, tea, milk]              | tea       | coffee    |
| [cake, pie]                      | pie       | cake      |
+----------------------------------+-----------+-----------+