How to parse JSON string recursively with openjson - sql-server-2016

Question

I have the following JSON data :
set #json = N'{
"Book":{
"IssueDate":"02-15-2019"
, "Detail":{
"Type":"Any Type"
, "Author":{
"Name":"Annie"
, "Sex":"Female"
}
}
, "Chapter":[
{
"Section":"1.1"
, "Title":"Hello world."
}
,
{
"Section":"1.2"
, "Title":"Be happy."
}
]
, "Sponsor":["A","B","C"]
}
}'
The expected result is
topKey Key Value
Book IssueDate 02-15-2019
Book Detail { "Type":"Any Type", "Author":{ "Name":"Annie" , "Sex":"Female"}
Book Chapter [{ "Section":"1.1", "Title":"Hello world." }, { "Section":"1.2", "Title":"Be happy." }]
Book Sponsor ["A","B","C"]
Detail Type Any Type
Detail Author { "Name":"Annie" ,"Sex":"Female"}
Author Name Annie
Author Sex Female
Chapter Section 1.1
Chapter Title Hello world
Chapter Section 1.2
Chapter Title Be happy.
I found that when the field "Value" is JSON, I need to keep parsing it.
So I created a function to do the parsing work but it returns '' which does not meet the requirement.
create function ParseJson(#json nvarchar(max))
returns #tempTable table ([key] nvarchar(max), [value] nvarchar(max))
as
begin
insert #tempTable
select
x.[key]
, x.[value]
from
openjson(#json) x
cross apply ParseJson(x.[value]) y
where ISJSON(x.[value])=1
end
A string may be passed to the function.
select * from ParseJson(#json)

Answer 1

I'm not sure if your expectation of the results is reasonable but clearly the returning table of your function doesn't match what you stated -- it lacks topKey column. For this reason, I'd rather aggregate the path of the hierarchy. Here we go:
create function ParseJson(
#parent nvarchar(max), #json nvarchar(max))
returns #tempTable table (
[key] nvarchar(max), [value] nvarchar(max))
as
begin
; with cte as (
select
iif(#parent is null, [key]
, concat(#parent, '.', [key])) [key]
, [value]
from
openjson(#json)
)
insert
#tempTable
select
x.*
from
cte x
union all
select
x.*
from
cte y
cross apply ParseJson(y.[key], y.[value]) x
where isjson(y.[value])=1
return
end
And the results: