T-SQL Json_modify to append a property to each object - sql-server

Question

I have a stored procedure that accepts a JSON string as input parameter. The input JSON string is like this:
[
{
"name":"Jhon",
"surname":"Smith",
"skills":["C#","VB.NET"]
},
{
"name":"Robert",
"surname":"Jhonson",
"skills":["T-SQL","Pascal"]
}
]
How can I add a unique GUID property to each principal object automatically?

Answer 1

Looking at your example data you already discovered this page of the documentation that tells you how to insert values with the json_modify() function. The examples on that page are written for a single "principal object".
If I interpret this correctly, then your sample has 2 principle objects. Using another page of the documentation shows how you can split that sample in rows with the openjson() function. You can then apply the json_modify() from the first documentation page on each row.
declare #var nvarchar(max) =
'[
{
"name":"Jhon",
"surname":"Smith",
"skills":["C#","VB.NET"]
},
{
"name":"Robert",
"surname":"Jhonson",
"skills":["T-SQL","Pascal"]
}
]';
select row_number() over(order by (select null)) as ObjNumber,
json_modify(j.value, '$.guid', convert(nvarchar(100), newid())) as ObjValue
from openjson(#var, '$') j
The result looks like this:
ObjNumber ObjValue
----------- ----------------------------------------------------
1 {
"name":"Jhon",
"surname":"Smith",
"skills":["C#","VB.NET"]
,"guid":"154C5581-588C-41AA-B292-BB6459F8F4DC"}
2 {
"name":"Robert",
"surname":"Jhonson",
"skills":["T-SQL","Pascal"]
,"guid":"46ACFDD6-58DE-4DB0-8D7A-9B1CCABFF8D8"}
Fiddle
To add the rows back together, just add for json path. This does however require a field alias (here MyObjects) that ends up in the output.
select json_modify(j.value, '$.guid', convert(nvarchar(100), newid())) as MyObjects
from openjson(#var, '$') j
for json path;
Output:
[{"MyObjects":{
"name":"Jhon",
"surname":"Smith",
"skills":["C#","VB.NET"]
,"guid":"FCED4D30-B2B0-460B-97FA-EDA820039572"}},{"MyObjects":{
"name":"Robert",
"surname":"Jhonson",
"skills":["T-SQL","Pascal"]
,"guid":"9FF02A70-0455-4E5C-8C11-27BB2688929D"}}]
Fiddle
To update the variable use the following code. Bonus: replace() removes the previously added field alias.
set #var = replace(
( select json_modify(j.value, '$.guid', convert(nvarchar(100), newid())) as MyObjects
from openjson(#var, '$') j
for json path ),
'"MyObjects":', '');
Final output for select #var:
[{{
"name":"Jhon",
"surname":"Smith",
"skills":["C#","VB.NET"]
,"guid":"66CB37D3-FAEF-4186-94D8-8AC0CF6EB1AC"}},{{
"name":"Robert",
"surname":"Jhonson",
"skills":["T-SQL","Pascal"]
,"guid":"564D6904-D981-40AC-BA9C-8B06015ACE50"}}]
Fiddle