JSON Hierarchy Problems - sql

Question

I don't have a recursive relationship here, but a problem of several child tables having the same parent, and having multiple records in each child table. Here's an example:
create table #Schedules (
ScheduleId int,
ScheduleName varchar(20)
);
create table #ScheduleThings (
ScheduleThingId int,
ScheduleId int,
Thing decimal(18,2));
create table #ScheduleOtherThings (
ScheduleOtherThingId int,
ScheduleId int,
OtherThing varchar(50));
I insert some typical sample data:
insert into #Schedules (
ScheduleId,
ScheduleName )
values
(1, 'A'),
(2, 'B');
insert into #ScheduleThings (
ScheduleThingId,
ScheduleId,
Thing )
values
(1, 1, 10.22),
(2, 1, 11.02),
(3, 1, 11.89),
(4, 2, 19.23),
(5, 2, 20.04),
(6, 2, 20.76),
(7, 2, 21.37);
insert into #ScheduleOtherThings (
ScheduleOtherThingId,
ScheduleId,
OtherThing )
values
(1, 1, 'Always'),
(2, 1, 'Sometimes'),
(3, 2, 'Seldom'),
(4, 2, 'Always'),
(5, 2, 'Never');
declare #results table (result xml);
I've then tried 2 similar approaches (3 or 4 actually), but here is one:
insert into #Results (
result )
select fr.result from (
select
s.ScheduleId as [schedules.schedule_id],
s.ScheduleName as [schedules.schedule_name],
st.ScheduleThingId as [schedules.schedule_things.schedule_thing_id],
st.Thing as [schedules.schedule_things.thing],
sot.ScheduleOtherThingId as [schedules.schedule_other_things.schedule_other_thing_id],
sot.OtherThing as [schedules.schedule_other_things.other_thing]
from #Schedules s
join #ScheduleThings st
on st.ScheduleId = s.ScheduleId
join #ScheduleOtherThings sot
on sot.ScheduleId = s.ScheduleId
where s.ScheduleId = 1
and st.ScheduleThingId < 3
for json path, root('schedules') ) fr(result) ;
select * from #Results;
This attempt gives me:
{
"schedules": [
{
"schedules": {
"schedule_id": 1,
"schedule_name": "A",
"schedule_things": {
"schedule_thing_id": 1,
"thing": 10.22
},
"schedule_other_things": {
"schedule_other_thing_id": 1,
"other_thing": "Always"
}
}
},
{
"schedules": {
"schedule_id": 1,
"schedule_name": "A",
"schedule_things": {
"schedule_thing_id": 1,
"thing": 10.22
},
"schedule_other_things": {
"schedule_other_thing_id": 2,
"other_thing": "Sometimes"
}
}
},
and removing 'schedules' from the dot notation entirely has no significant impact:
{
"schedules": [
{
"schedule_id": 1,
"schedule_name": "A",
"schedule_things": {
"schedule_thing_id": 1,
"thing": 10.22
},
"schedule_other_things": {
"schedule_other_thing_id": 1,
"other_thing": "Always"
}
},
{
"schedule_id": 1,
"schedule_name": "A",
"schedule_things": {
"schedule_thing_id": 1,
"thing": 10.22
},
"schedule_other_things": {
"schedule_other_thing_id": 2,
"other_thing": "Sometimes"
}
},
What I need (and what I think is the proper JSON structure) is like:
{
"schedules": [
{
"schedule_id": 1,
"schedule_name": "A",
"schedule_things": [
{
"schedule_thing_id": 1,
"thing": 10.22
},
{
"schedule_thing_id": 2,
"thing": 11.02
},
]
"schedule_other_things": [
{
"schedule_other_thing_id": 1,
"other_thing": "Always"
},
{
"schedule_other_thing_id": 2,
"other_thing": "Sometimes"
}
]
}
]
}
In other words, the attributes of the parent 'Schedule' record appear one time, an object of ScheduleThings follows, including all child ScheduleThings, followed by an object of ScheduleOtherThings, etc.
I don't understand yet why my dot specifications don't make it clear which attributes belong to the root object, and therefore that I don't need those attributes repeated. But, I especially don't understand why the entire dataset is flattened--even when I think I've used the dot notation to make the parent-child relationships very explicit.

Answer 1

You could try nesting the calls to for json
Such as...
select
fr.result
from
(
select
s.ScheduleId as [schedules.schedule_id],
s.ScheduleName as [schedules.schedule_name],
(
SELECT ScheduleThingId, Thing
FROM #ScheduleThings
WHERE ScheduleId = s.ScheduleId
AND ScheduleThingId < 3
FOR JSON PATH
)
AS [schedules.schedule_things],
(
SELECT ScheduleOtherThingId, OtherThing
FROM #ScheduleOtherThings
WHERE ScheduleId = s.ScheduleId
FOR JSON PATH
)
AS [schedules.schedule_other_things]
from
#Schedules s
where
s.ScheduleId = 1
for json path, root('schedules')
)
fr(result) ;
Demo : https://dbfiddle.uk/?rdbms=sqlserver_2019&fiddle=e9a9c55b2daaac4e0f48d52a87bfede9