Sum items in a TSQL JSON column - tsql

Question

Lets say I have a table and in a "data" NVARCHAR(MAX) column, I have this JSON:
[
{
"room": "kitchen",
"items": [
{
"name": "table",
"price": 100
}
]
},
{
"room": "bedroom",
"items": [
{
"name": "bed",
"price": 250
},
{
"name": "lamp",
"price": 50
}
]
},
{
"room": "bathroom",
"items": [
{
"name": "toilet",
"price": 101
},
{
"name": "shower",
"items": [
{
"name": "shower curtain",
"price": 10
},
{
"name": "shower head",
"price": 40
}
]
}
]
}
]
Using TSQL, can I somehow SUM all prices in the JSON? Please notice that my "price" is in different levels in the JSON file.
And furthermore, can I make a computed column that will SUM all the prices in the JSON column?

Answer 1

In JSon you would have to treat all nodes and check if another sublevel including "Price" exists. As text it is easier. This example is for one cell.
The idea above to insert the result to another column in the table is a good one.
You can implement a trigger after every INSERT / UPDATE to calculate instead of a computed column.
declare #str varchar(4000)='[ { "room": "kitchen", "items": [ { "name": "table", "price": 100 } ] }, { "room": "bedroom", "items": [ { "name": "bed", "price": 250 }, { "name": "lamp", "price": 50 } ] }, { "room": "bathroom", "items": [ { "name": "toilet", "price": 101 }, { "name": "shower", "items": [ { "name": "shower curtain", "price": 10 }, { "name": "shower head", "price": 40 } ] } ] } ]'
, #sub varchar(15);
drop table if exists #prices;
create table #prices(price int);
WHILE patindex('%"price": %',#str) > 0
begin
SELECT #sub=SUBSTRING(#str, patindex('%"price": %',#str), 15)
WHILE PatIndex('%[^0-9]%', #sub) > 0
SET #sub = Stuff(#sub, PatIndex('%[^0-9]%', #sub), 1, '');
insert into #prices select try_cast(#sub as int);
SET #str = Stuff(#str, patindex('%"price": %',#str), 15, '');
end;
select sum(price) from #prices;