Multip Choice Question - Postgres Join two tables - sql

Question

I am new to SQL previously we were using MongoDB and now we have shifted to Postgres. basically, we have 2 tables of Questions and Options. Each question can have multiple option so I design the database just like below table.
Table : dialogues
dialogue_id
dialogue_text
...
Table : options
option_id
option_name
dialogue_id ( which is FK for table question)
Now I am trying to get all the questions with their options. I have tried inner join like this
SELECT options.option_name, dialogues.*
FROM options INNER JOIN dialogues ON dialogues.dialogue_id = options.dialogue_id)
But it's not what I wanted.
Just to give you an example in Mongo we have used this query
const aggregateQuery = [
{
$lookup: {
from: "options", // The collection you want to join to
localField: "_id", // The field in orders you want to join on
foreignField: "question_id", // The field in products you want to join on
as: "options" // What you want to call the array that stores the joined documents from products
}
},
}
]
const questionList = await questionModel.aggregate(aggregateQuery)
In result I wanted all the dialogue along with field called "options" which contains all the relevant options from table "options".
let me share the final JSON that I get from mongo.
[
{
"_id": "yyyyy",
"question": "What is your gender?",
"options": [
{
"_id": "xxxxx",
"option": "Male",
"question_id": "yyyyy",
"created_at": "2020-07-04T05:57:00.293Z",
"updated_at": "2020-07-04T05:57:00.293Z"
},
{
"_id": "xxxx",
"option": "Female",
"question_id": "yyyyy",
"created_at": "2020-07-04T05:57:00.293Z",
"updated_at": "2020-07-04T05:57:00.293Z"
}
]
}
]
can anybody help ?

Answer 1

This may be your solution.
select jsonb_agg(to_jsonb(t)) from
(
select
d.dialogue_id "_id",
d.dialogue_text "question",
(
select
jsonb_agg(jsonb_build_object('_id', o.option_id, 'option', o.option_name))
from options o
where o.dialogue_id = d.dialogue_id
) "options"
from dialogues d
) t;
Here is a JOIN/GROUP BY version
select jsonb_agg(to_jsonb(t)) from
(
select
d.dialogue_id "_id",
d.dialogue_text "question",
jsonb_agg(jsonb_build_object('_id', o.option_id, 'option', o.option_name)) "options"
from dialogues d inner join options o using (option_id)
group by d.dialogue_id, d.dialogue_text
) t;