Postgres join jsonb column - postgresql

Question

I have a left table that looks like this
+-----------+-----------------------+
| name | interests |
+-----------+-----------------------+
| Jason | ["sports", "food"] |
+-----------+-----------------------+
And another table that has the interest information.
+-----------+----------------------------+
| interest | items |
+-----------+----------------------------+
| sports | ["football", "swimming"] |
+-----------+----------------------------+
| food | ["pasta", "bread"] |
+-----------+----------------------------+
| news | ["BBC", "New York Times"] |
+-----------+----------------------------+
How could I now make a query so that I can obtain an output like this?
Basically something like in Python, we would iterate over the interests and get all the items belong to those interests.
Many thanks.
+-----------+---------------------------------------------+
| name | items |
+-----------+---------------------------------------------+
| Jason | ["football", "swimming", "pasta", "bread"] |
+-----------+---------------------------------------------+

Answer 1

This is really a questionable database design. A traditional many-to-many table would probably make more sense.
However, to achieve what you want, you need to unnest the all elements from the interest table for all interests from the person table. Then aggregate them back into a JSON array:
select p.name,
i.interests
from person p
left join lateral (
select jsonb_agg(ix.item) as interests
from interest i
cross join jsonb_array_elements(i.items) as ix(item)
where p.interests ? i.interest
) as i on true
Online example
A slightly more compact version can be achieved, by defining your own aggregate that appends multiple jsonb values (rather than creating an array of arrays as jsonb_agg() would do if done on the "raw" arrays).
create aggregate jsonb_append_agg(jsonb)
(
sfunc = jsonb_concat(jsonb, jsonb),
stype = jsonb
);
Then you can use it like this:
select p.name,
i.interests
from person p
left join lateral (
select jsonb_append_agg(i.items) as interests
from interest i
where p.interests ? i.interest
) as i on true;