how to filter fields from jsonb type column while querying on postgresql - postgresql

Question

Here is my table (simplified, only significant columns):
CREATE TABLE details(
id serial primary key,
name text,
Address jsonb );
And some sample Data
# Select * from details
id | name | Address
----+----------+-----------------------------------------------------------
1 | Batman | {"city":"Gotham City","street":"1007 Mountain Drive"}
2 | Superman | {"city":"Metropolis","street":"344 Clinton Street"}
3 | Flash | {"city":"Central City","street":"122 Englewood street"}
Now I would like to select only name and City field of Address, Query would be
Select name, Address -> 'city' as Address from details
name | Address
----------+------------------
Batman | "Gotham City"
Superman | "Metropolis"
Flash | "Central City"
But I want it to be filtered as shown below.
name | Address
----------+-------------------------
Batman | {"city":"Gotham City"}
Superman | {"city":"Metropolis"}
Flash | {"city":"Central City"}
Is it possible to select only some fields from jsonb type column? If it is possible then what would be the query ?

Answer 1

If you want to include only 1 field, your query can be fairly easy:
select name, jsonb_build_object('city', address -> 'city') address
from details
However, if you want to include multiple fields, things will get complex. You could f.ex. remove unwanted keys one-by-one with the - operator, like: jsonb_column - 'key1' - 'key2':
select name, address - 'street' address
from details
But this will only work, when you have a fairly few fields inside of the JSON column (and they are well defined).
If you want a general solution, you should use some aggregation:
select name, (select jsonb_object_agg(e.key, e.value)
from jsonb_each(address) e
where e.key in ('city')) address
from details