BigQuery ARRAY_AGG(STRUCT) splitting values basing on column value - google-bigquery

Question

I have a BigQuery table like this:
+------+------------+----------+-------+--------+
| Name | Date | Category | Value | Number |
+------+------------+----------+-------+--------+
| John | 2019-01-03 | Cat1 | AA | 10 |
| John | 2019-01-03 | Cat1 | AB | 11 |
| John | 2019-01-03 | Cat2 | NN | 12 |
| John | 2019-01-03 | Cat2 | MM | 13 |
+------+------------+----------+-------+--------+
The first 2 columns are the key identifier and I need to ARRAY/GROUP the rows basing on those 2 columns.
Here is the sample statement:
WITH data AS (
SELECT "John" name, DATE("2019-01-03") date, "cat1" category, "AA" value, 10 number
UNION ALL
SELECT "John", DATE("2019-01-03"), "cat1", "AB", 11
UNION ALL
SELECT "John", DATE("2019-01-03"), "cat2", "NN", 12
UNION ALL
SELECT "John", DATE("2019-01-03"), "cat2", "MM", 13
)
SELECT * FROM data
The basic version of the query is very simple:
SELECT
name,
date,
ARRAY_AGG(
STRUCT<category STRING, value STRING, number INT64>(category,value,number)
) AS items
FROM data
GROUP BY 1,2
but in my case I need to distinct the values (on 2 different columns) the value-number grouped values based on category column
I don't know if a dynamic column definition can be made, basing on the DISTINCT values of the category values, but in a simplier case I can use fixed values cat1 and cat2
Here an example of the output I described:
+------+------------+--------------------+---------------------+--------------------+---------------------+
| Name | Date | cat1_grouped.value | cat1_grouped.number | cat2_grouped.value | cat2_grouped.number |
+------+------------+--------------------+---------------------+--------------------+---------------------+
| John | 2019-01-03 | AA | 10 | NN | 12 |
| | | AB | 11 | MM | 13 |
| | | | | | |
+------+------------+--------------------+---------------------+--------------------+---------------------+

Answer 1

Below is working example - for BigQuery Standard SQL
#standardSQL
WITH `project.dataset.table` AS (
SELECT 'John' name, DATE '2019-01-03' dt, 'Cat1' category, 'AA' value, 10 number UNION ALL
SELECT 'John', '2019-01-03', 'Cat1', 'AB', 11 UNION ALL
SELECT 'John', '2019-01-03', 'Cat2', 'NN', 12 UNION ALL
SELECT 'John', '2019-01-03', 'Cat2', 'MM', 13
)
SELECT name, dt,
ARRAY_CONCAT_AGG(IF(category = 'Cat1', arr, [])) cat1_grouped,
ARRAY_CONCAT_AGG(IF(category = 'Cat2', arr, [])) cat2_grouped
FROM (
SELECT name, dt, category,
ARRAY_AGG(STRUCT<value STRING, number INT64>(value, number)) arr
FROM `project.dataset.table`
GROUP BY name, dt, category
)
GROUP BY name, dt
with result
Row name dt cat1_grouped.value cat1_grouped.number cat2_grouped.value cat2_grouped.number
1 John 2019-01-03 AA 10 NN 12
AB 11 MM 13