Casting an array of strings to an array of integers - postgresql

Question

How can I cast an array of string into an array of integers?
Below is my array
["6", "5"]
I want convert into int array
[6, 5]

Answer 1

demo:db<>fiddle
SELECT
array_agg(elems::int)
FROM unnest(ARRAY['5', '6']) as elems
Expand the array into one record per element
Reaggregate cast integer values
To ensure the original order, you need to add WITH ORDINALITY, which adds an index to the original array:
SELECT
array_agg(elems.value::int ORDER BY elems.index)
FROM unnest(ARRAY['5', '6']) WITH ORDINALITY as elems(value, index)
If you have a JSON array instead, the algorithm is the same, only the used functions have different names:
SELECT
json_agg(elems.value::int ORDER BY elems.index)
FROM json_array_elements_text('["5", "6"]'::json) WITH ORDINALITY as elems(value, index)
EDIT: According to comment:
this is my query. SELECT data->>'pid' FROM user_data where
data->>'pid' is not null How can I update pid to array of integers ?
demo:db<>fiddle
You have to expand and reaggregate nonetheless:
SELECT
json_agg(elems::int) -- 2
FROM user_data,
json_array_elements_text(data -> 'pid') as elems -- 1
WHERE data->>'pid' IS NOT NULL
GROUP BY id

Answer 2

You can’t “cast”, but you can get something very close to a cast:
array(select unnest(myArray)::int)
As a testable query:
select array(select unnest(array['5', '6'])::int)
See live demo.
When applying to a column of a selected table:
select
array(select unnest(myArrayCol)::int)
from myTable
See live demo.
This syntax preserves order.