SQL - 使用“IGNORE NULLS”时数组中包含的 NULL 值

Question

我遇到了一个问题，即 ARRAY_AGG 使用“IGNORE NULLS”传递，但 null 值仍包含在 output 中。

是因为我在 ARRAY_AGG 中有 STRUCT 吗？

有人可以告诉我我做错了什么吗？

示例代码：

WITH t AS (
  SELECT 1 as batch_id, 1 as sensor_id, 1 as product_part_id, 2 as defect_id,  5 as count_defects, '2018-7-1' as event_date
  UNION ALL SELECT 1 as batch_id, 2 as sensor_id, 1 as product_part_id, 2 as defect_id,  6 as count_defects, '2018-7-1' as event_date
  UNION ALL SELECT 1 as batch_id, 2 as sensor_id, 2 as product_part_id, 3 as defect_id,  7 as count_defects, '2018-7-1' as event_date
  UNION ALL SELECT 1 as batch_id, 3 as sensor_id, 2 as product_part_id, 3 as defect_id,  8 as count_defects, '2018-7-1' as event_date
  UNION ALL SELECT 1 as batch_id, 3 as sensor_id, 2 as product_part_id, 4 as defect_id,  9 as count_defects, null as event_date
  UNION ALL SELECT 1 as batch_id, 3 as sensor_id, 3 as product_part_id, 5 as defect_id, 10 as count_defects, '2018-7-1' as event_date
),
defect_nesting as (
  SELECT 
    batch_id, 
    sensor_id, 
    product_part_id, 
    array_agg(STRUCT(defect_id, count_defects, event_date) IGNORE NULLS ORDER BY defect_id) defectInfo
  FROM t 
  GROUP BY 1, 2, 3
  ),

product_nesting as (  
  SELECT 
    batch_id,
    sensor_id,
    array_agg(STRUCT(product_part_id, defectInfo) IGNORE NULLS ORDER BY product_part_id) productInfo
  FROM defect_nesting
  GROUP BY 1,2
)

SELECT 
  batch_id,
  array_agg(STRUCT(sensor_id, productInfo) IGNORE NULLS ORDER BY sensor_id) sensorInfo
FROM product_nesting
GROUP BY 1

样品 output：

我的最终结果将只是空白而不是空值。

Answer 1

嗨，你可以试试这个查询吗？

询问：

WITH t AS (
  SELECT 1 as batch_id, 1 as sensor_id, 1 as product_part_id, 2 as defect_id,  5 as count_defects, '2018-7-1' as event_date
  UNION ALL SELECT 1 as batch_id, 2 as sensor_id, 1 as product_part_id, 2 as defect_id,  6 as count_defects, '2018-7-1' as event_date
  UNION ALL SELECT 1 as batch_id, 2 as sensor_id, 2 as product_part_id, 3 as defect_id,  7 as count_defects, '2018-7-1' as event_date
  UNION ALL SELECT 1 as batch_id, 3 as sensor_id, 2 as product_part_id, 3 as defect_id,  8 as count_defects, '2018-7-1' as event_date
  UNION ALL SELECT 1 as batch_id, 3 as sensor_id, 2 as product_part_id, 4 as defect_id,  9 as count_defects, null as event_date
  UNION ALL SELECT 1 as batch_id, 3 as sensor_id, 3 as product_part_id, 5 as defect_id, 10 as count_defects, '2018-7-1' as event_date
),
t2 as (
SELECT 
  * except(event_date), 
  ifnull(event_date,'') as event_date 
from t
),
defect_nesting as (
  SELECT 
    batch_id, 
    sensor_id, 
    product_part_id, 
    array_agg(STRUCT(defect_id, count_defects, event_date) ORDER BY defect_id) defectInfo
  FROM t2 
  GROUP BY 1, 2, 3
  ),

product_nesting as (  
  SELECT 
    batch_id,
    sensor_id,
    array_agg(STRUCT(product_part_id, defectInfo) ORDER BY product_part_id) productInfo
  FROM defect_nesting
  GROUP BY 1,2
)

SELECT 
  batch_id,
  array_agg(STRUCT(sensor_id, productInfo) ORDER BY sensor_id) sensorInfo
FROM product_nesting
GROUP BY 1

我添加了一个新的 CTE，它在 event_date 列中用空白替换空值，并将此表用于查询的 rest。 （还删除了忽略空值，因为它只是排除了 ricco D 提到的空值。

Output：

（如果其他列也应该有 null 值，您可以将相同的查询/逻辑应用于其他列 (IFNULL)）