Postgres 11

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CREATE TABLE mydata(jsondata) AS (VALUES ('{"a":1}'::jsonb), ('{"b":2}'::jsonb));

SELECT * 
FROM mydata

SELECT 2

jsondata

{"a": 1}

{"b": 2}

SELECT 2

SELECT 
    *
FROM mydata,
    jsonb_each(jsondata) AS elems

jsondata
key
value

{"a": 1}
a
1

{"b": 2}
b
2

SELECT 2

SELECT 
    jsonb_object_agg(key, value)
FROM mydata,
    jsonb_each(jsondata) AS elems

jsonb_object_agg

{"a": 1, "b": 2}

SELECT 1