Построить запрос для вложенной структуры в bigquery

Question

У меня был следующий фрагмент кода

WITH sequences AS
  (SELECT 1 AS id, [STRUCT(0 AS a, 1 AS b)] AS some_numbers
   UNION ALL SELECT 2 AS id, [STRUCT(2 AS b, 4 AS a)] AS some_numbers
   UNION ALL SELECT 3 AS id, [STRUCT(5 AS b, 3 AS a), STRUCT (7 AS b, 4 AS a)]
     AS some_numbers)
SELECT id AS matching_rows
FROM sequences
WHERE EXISTS (SELECT 1
              FROM UNNEST(some_numbers)
              WHERE b > 3);

И я получил следующий вывод

Row	matching_rows	
1	    2
2       3

Согласно условию where результат должен быть только 3-й строкой. Почему это также показывает 2-й ряд? ..

Answer 1

Структурные поля объединяются по позиции, а не по имени.Итак, это:

WITH sequences AS
  (SELECT 1 AS id, [STRUCT(0 AS a, 1 AS b)] AS some_numbers
   UNION ALL SELECT 2 AS id, [STRUCT(2 AS b, 4 AS a)] AS some_numbers
   UNION ALL SELECT 3 AS id, [STRUCT(5 AS b, 3 AS a), STRUCT (7 AS b, 4 AS a)]
     AS some_numbers)
SELECT id AS matching_rows
FROM sequences
WHERE EXISTS (SELECT 1
              FROM UNNEST(some_numbers)
              WHERE b > 3);

эквивалентно этому:

WITH sequences AS
  (SELECT 1 AS id, [STRUCT(0 AS a, 1 AS b)] AS some_numbers
   UNION ALL SELECT 2 AS id, [STRUCT(2 AS a, 4 AS b)] AS some_numbers
   UNION ALL SELECT 3 AS id, [STRUCT(5 AS a, 3 AS b), STRUCT (7 AS a, 4 AS b)]
     AS some_numbers)
SELECT id AS matching_rows
FROM sequences
WHERE EXISTS (SELECT 1
              FROM UNNEST(some_numbers)
              WHERE b > 3);

Кроме первого запроса в объединении, вы также можете удалить псевдонимы AS <name>, так как они невлияет на результат.