Aggregate concatenate jsonb arrays

Question

Having a table named example_table with one column named example_column of type JSONB and every value in the column being an array.

Having the values in 2 rows be: [1, 2] and [3]

How can I aggregate-concatenate the values in example_column?

The result should be: [1, 2, 3]

I tried using:

select json_agg(example_column) from example_table

but that returns [[1, 2,], [3]]

Answer 1

Use the function jsonb_array_elements(example_column), example:

with example_table(example_column) as (
values
    (jsonb '[1, 2]'),
    (jsonb '[3]')
)

select jsonb_agg(value)
from example_table
cross join jsonb_array_elements(example_column) 

jsonb_agg 
-----------
 [1, 2, 3]
(1 row)

Update. You can define the sort order of aggregated elements and/or remove duplicates, e.g.:

with example_table(id, example_column) as (
values
    (1, jsonb '[1, 2]'),
    (2, jsonb '[3]'),
    (3, jsonb '[3, 1]')
)

select 
    jsonb_agg(value order by id) as agg1,
    jsonb_agg(value order by value) as agg2,
    jsonb_agg(distinct value order by value) as agg3
from example_table
cross join jsonb_array_elements(example_column) 

      agg1       |      agg2       |   agg3    
-----------------+-----------------+-----------
 [1, 2, 3, 3, 1] | [1, 1, 2, 3, 3] | [1, 2, 3]
(1 row)