Updating jsonb field using concatenation operator in postgres - postgresql

Question

I am trying to update a jsonb field which has nested json objects in it using the concatenation operator in postgres as in dbfidde
But, it removes all other fields for example if I run the below script
UPDATE t
SET details = details || '{"name": {"firstname": "newname"},"address":{"city":"newCity"}}'
WHERE details -> 'name' ->>'firstname'='myname'
It removes the "lastname" field from the updated field
I tried updating with jsonb_set too but I am not sure how I can update multiple properties using jsonb_set

Answer 1

The || way does not work because the new name value is {"firstname":"newname"}. This replaces the complete old value {"firstname": "myname","lastname":"last"} and so removes the lastname attribute. This way only works if you are working on the toplevel fields. But you want to update the nested objects.
In that case I see no way around two separate calls of jsonb_set(). One possible way is to nest them:
demo:db<>fiddle
UPDATE t
SET details =
jsonb_set(
jsonb_set(details, '{name,firstname}','"newname"'),
'{address,city}',
'"newCity"'
)
WHERE details -> 'name' ->> 'firstname' = 'myname';
Updating the original details field; setting the new firstname value through the given path '{name,firstname}'
The resulting JSON object can be used directly for a following update of the city value using the same way.