Get average of JSONB array in postgres - sql

Question

I have a postgres table 'games' containing different scores for a game. I want to query all the games and have the average score of all the scores for that specific game. I tried a lot of different queries but I always get in trouble because of the JSONB datatype. The data of the games are saved in JSONB format and the games table looks like this:
gameID gameInfo
---------------------------------------------------------------
1 {
"scores": [
{
"scoreType": "skill",
"score": 1
},
{
"scoreType": "speed",
"score": 3
},
{
"scoreType": "strength",
"score": 2
}
]}
2 {
"scores": [
{
"scoreType": "skill",
"score": 4
},
{
"scoreType": "speed",
"score": 4
},
{
"scoreType": "strength",
"score": 4
}
]}
3 {
"scores": [
{
"scoreType": "skill",
"score": 1
},
{
"scoreType": "speed",
"score": 3
},
{
"scoreType": "strength",
"score": 5
}
]}
Expected output:
GameId
AverageScore
1
2
2
4
2
3
What query can I use to get the expected output?

Answer 1

Extract JSONB representing an array, use a JSONB function to get array of JSONB, extract the string value.
select gameid, avg(score::int) s
from (
select gameid, jsonb_array_elements(gameInfo #>'{scores}') ->'score' score
from foo
) t
group by gameid
order by gameid

Answer 2

Also you can use lateral join in next way:
select gameID, avg((s->>'score')::int) avg_score
from g, lateral jsonb_array_elements((gameInfo->>'scores')::jsonb) s
group by gameID
;
SQL editor online
Result:
+========+====================+
| gameid | avg_score |
+========+====================+
| 3 | 3.0000000000000000 |
+--------+--------------------+
| 2 | 4.0000000000000000 |
+--------+--------------------+
| 1 | 2.0000000000000000 |
+--------+--------------------+