Select - Oracle JSON Object - Join - json

Question

I have a requirement to select column values in Oracle in a JSON structure. Let me explain the requirement in detail
We have a table called "dept" that has the following rows
There is another table called "emp" that has the following rows
The output we need is as follows
{"Data": [{
"dept": "Sports",
"City": "LA",
"employees": {
"profile":[
{"name": "Ben John", "salary": "15000"},
{"name": "Carlos Moya", "salary": "19000"}]
}},
{"dept": "Sales",
"City": "Miami",
"employees": {
"profile":[
{"name": "George Taylor", "salary": "9000"},
{"name": "Emma Thompson", "salary": "8500"}]
}}
]
}
The SQL that I issued is as follows
select json_object('dept' value b.deptname,
'city' value b.deptcity,
'employees' value json_object('employee name' value a.empname,
'employee salary' value a.salary)
format json) as JSONRETURN
from emp a, dept b where
a.deptno=b.deptno
However, the result looks like the following and not what we expected.
Please note the parent data is repeated. What is the mistake I am making?
Thanks for the help
Bala

Answer 1

You can do something like this. Note the multiple (nested) calls to json_object and json_arrayagg. Tested in Oracle 12.2; other versions may have other tools that can make the job easier.
select json_object(
'Data' value
json_arrayagg(
json_object (
'dept' value deptname,
'City' value deptcity,
'employees' value
json_object(
'profile' value
json_arrayagg(
json_object(
'name' value empname,
'salary' value salary
) order by empid -- or as needed
)
)
) order by deptno -- or as needed
)
) as jsonreturn
from dept join emp using (deptno)
group by deptno, deptname, deptcity
;