PostgreSQL query : distinct count of jsonb values column - mysql

Question

I have a table with the name mainapp_project_data which has a jsonb column project_user_data
TABLE
public | mainapp_project_data | table | admin
select project_user_data from mainapp_project_data;
project_user_data
-----------------------------------------------------------------------------------------------------------------
[{"name": "john", "age": "21", "gender": "M"}, {"name": "randy", "age": "23", "gender": "M"}]
[{"name": "donald", "age": "31", "gender": "M"}, {"name": "wick", "age": "32",
"gender": "M"}]
[{"name": "orton", "age": "18", "gender": "M"}, {"name": "russel", "age": "55",
"gender": "M"}]
[{"name": "angelina", "age": "open", "gender": "F"}, {"name": "josep", "age": "21",
"gender": "M"}]
(4 rows)
(END)
I would like to count the distinct values of keys gender and age of JSON.
output format : [{key:count(repeated_values)}]
filtering on `gender` : [{"M":7},{"F":1}]
filtering on `age` : [{"21":2},{"23":1},{"31":1}.....]

Answer 1

WITH flat AS (
SELECT
kv.key,
-- make into a JSON object with a single value and count, e.g., '{"M": 7}'
jsonb_build_object(kv.value, COUNT(*)) AS val_count
FROM mainapp_project_data AS mpd
-- Flatten the JSON arrays into single objects per row
CROSS JOIN LATERAL jsonb_array_elements(mpd.project_user_data) AS unarrayed(udata)
-- Convert to a long, flat list of key-value pairs
CROSS JOIN LATERAL jsonb_each_text(unarrayed.udata) AS kv(key, value)
GROUP BY kv.key, kv.value
)
SELECT
-- de-deplicated object keys
flat.key,
-- aggregation of all values and counts per key
jsonb_agg(flat.val_count) AS value_counts
FROM flat
GROUP BY flat.key
Returns
key | value_counts
--------+---------------------------------------------------------------------------------------------------------------------
gender | [{"M": 7}, {"F": 1}]
name | [{"josep": 1}, {"russel": 1}, {"orton": 1}, {"donald": 1}, {"wick": 1}, {"john": 1}, {"randy": 1}, {"angelina": 1}]
age | [{"18": 1}, {"32": 1}, {"21": 2}, {"23": 1}, {"open": 1}, {"31": 1}, {"55": 1}]
This will provide any key-value pair instance count. If you just want genders and ages, just add a where clause before the first GROUP BY clause.
WHERE kv.key IN ('gender', 'age')

Answer 2

Does something like this work for you?
postgres=# select count(*), (foo->'gender')::text as g from (select json_array_elements(project_user_data) as foo from mainapp_project_data) as j group by (foo->'gender')::text;
count | g
-------+-----
7 | "M"
1 | "F"
(2 rows)
postgres=# select count(*), (foo->'age')::text as g from (select json_array_elements(project_user_data) as foo from mainapp_project_data) as j group by (foo->'age')::text;
count | g
-------+--------
2 | "21"
1 | "32"
1 | "open"
1 | "23"
1 | "18"
1 | "55"
1 | "31"
(7 rows) ```