Getting response in desired format with postgreSQL - sql

Question

There are a bunch of tables in my database named courses, topics, subtopics, assessments.
One course can have multiple topics. One topic can have multiple subtopics. One topic can have multiple assessments.
There is a query I'm trying to implement in which I need a response in a specific format. For which aggregation has been used. I'm getting the desired result except for assessments.
The format I want is an array of courses. For each course, there is an array of topics. For each topic, there is an array of subtopics. This much I'm able to achieve. Now, I want for each topic an array of assessments just like subtopics which I'm unable to achieve.
The Code:
select courses.course_id as id, courses.course_name as name, courses.course_duration as
duration, courses.course_description as description,
jsonb_agg(
jsonb_build_object(
'id', topics.topic_id,
'name', topics.topic_name,
'duration', topics.topic_duration,
'sequence_no', topics.sequence_no,
'description', topics.topic_description,
'subtopics', subtopic.subtopics,
'assessment_id', assessments.id
)
order by topics.topic_id
) topics
from courses
left join topics on courses.course_id = topics.course_id
cross join lateral (
select jsonb_agg(
jsonb_build_object(
'id', subtopics.subtopic_id,
'name', subtopics.subtopic_name,
'assignment_id', subtopics.assignment_id,
'homework_id', subtopics.homework_id,
'on_free_trial', subtopics.on_free_trial
)
order by subtopics.subtopic_id
) subtopics
from subtopics
where subtopics.topic_id = topics.topic_id
) subtopic
left join assessments on assessments.topic_id = topics.topic_id
cross join lateral (
select jsonb_agg(
jsonb_build_object(
'id', assessments.id
)
order by assessments.id
) assessments
from assessments
where assessments.topic_id = topics.topic_id
) assessment
group by courses.course_id
order by courses.course_id
The output is as follows:
{
"Response": [
{
"id": 1,
"name": "Data Structures and Algorithms",
"duration": 32,
"description": "A data structure is a named location that can be used to store and organize data. And, an algorithm is a collection of steps to solve a particular problem. Learning data structures",
"topics": [
{
"id": 1,
"name": "ARRAYS AND VECTORS",
"duration": 7,
"subtopics": [
{
"id": 1,
"name": "Pre-Computations in Array",
"homework_id": 1,
"assignment_id": 1,
"on_free_trial": null
},
{
"id": 2,
"name": "Pre-Computations",
"homework_id": 1,
"assignment_id": 2,
"on_free_trial": null
}
],
"description": "Static and Dynamic Arrays, Pre-Computations, Array Rotations, Sliding Window Technique, Bucketization Technique etc.",
"sequence_no": 1,
"assessment_id": 2
},
{
"id": 1,
"name": "ARRAYS AND VECTORS",
"duration": 7,
"subtopics": [
{
"id": 1,
"name": "Pre-Computations in Array",
"homework_id": 1,
"assignment_id": 1,
"on_free_trial": null
},
{
"id": 2,
"name": "Pre-Computations",
"homework_id": 1,
"assignment_id": 2,
"on_free_trial": null
}
],
"description": "Static and Dynamic Arrays, Pre-Computations, Array Rotations, Sliding Window Technique, Bucketization Technique etc.",
"sequence_no": 1,
"assessment_id": 1
},
{
"id": 2,
"name": "MATHS",
"duration": 7,
"subtopics": null,
"description": "Modular arithmetic, Combinatorics, Euclid’s Algorithm for GCD, Primality Testing : Sieve of Eratosthenes, Fast Factorization, Catalan Numbers",
"sequence_no": 2,
"assessment_id": null
}
]
},
{
"id": 2,
"name": "OPERATING SYSTEMS",
"duration": 30,
"description": "An exhaustive collection of all the must-know concepts of Operating Systems",
"topics": [
{
"id": 100,
"name": "Threads and Processes",
"duration": 4,
"subtopics": [
{
"id": 5,
"name": "Basics of Threads and Processes",
"homework_id": 100,
"assignment_id": 100,
"on_free_trial": null
},
{
"id": 6,
"name": "Inter Process Communication",
"homework_id": null,
"assignment_id": null,
"on_free_trial": null
}
],
"description": "Difference b/w Threads and Processes, PCB",
"sequence_no": 1,
"assessment_id": null
},
{
"id": 101,
"name": "Memory Management",
"duration": 3,
"subtopics": [
{
"id": 7,
"name": "Logical And Physical Memory",
"homework_id": 101,
"assignment_id": 101,
"on_free_trial": null
}
],
"description": "Logical and Physical Memory, Paging, Fragmentation",
"sequence_no": 2,
"assessment_id": null
}
]
},
{
"id": 3,
"name": "Python",
"duration": 4,
"description": "Basics of python language.",
"topics": [
{
"id": 3,
"name": "Python list",
"duration": 1,
"subtopics": null,
"description": "Basics of python.",
"sequence_no": 1,
"assessment_id": null
}
]
}
]
}
As one can see the topic is getting repeated because of assessment_id. I want it to be structured in form of an array Or array of objects as subtopics are.

Answer 1

You forgot to use the assessments in the json_build_object as you did with the subtopics:
select courses.course_id as id, courses.course_name as name, courses.course_duration as
duration, courses.course_description as description,
jsonb_agg(
jsonb_build_object(
'id', topics.topic_id,
'name', topics.topic_name,
'duration', topics.topic_duration,
'sequence_no', topics.sequence_no,
'description', topics.topic_description,
'subtopics', subtopic.subtopics,
'assessments', assessments.assessments
)
order by topics.topic_id
) topics
...