Accessing an array object from JSON by index-variable - json

Question

I want to access over an array object in JSON by index with a variable. Consider the following code:
declare #pjson nvarchar(max)='{
"store":{
"storeId": 100,
"name": "TEST",
"lastUpdatedBy": "MULE",
"location": {
declare #pjson nvarchar(max)='{
"store":{
"storeId": 100,
"name": "TEST",
"lastUpdatedBy": "MULE",
"location": {
"addresses": [
{
"addressType": "MAIN",
"name": "Name1",
"name2": "Name2",
"address": "Address1",
"address2": "Address2",
"city": "City",
"lastUpdateBy": "MULE"
},
{
"addressType": "SECONDARY",
"name": "Name1",
"name2": "Name2",
"address": "Address1",
"address2": "Address2",
"city": "City",
"lastUpdateBy": "MULE"
},
{
"addressType": "BILLING",
"name": "Name1",
"name2": "Name2",
"address": "Address1",
"address2": "Address2",
"city": "City",
"lastUpdateBy": "MULE"
}
]
}
}
}'
Declare #counter1 INT = 0;
Print JSON_VALUE(#pjson,N'lax $.store.location.addresses[#counter1].addressType')
I get an error:
JSON path is not properly formatted. Unexpected character '#' is found
at position 31.
If I try directly by passing number as
Declare #counter1 INT = 0;
Print JSON_VALUE(#pjson,N'lax $.store.location.addresses[0].addressType')
I get the expected result
MAIN
Is there something that I am missing while passing the variable?

Answer 1

I don't think that you can use a T-SQL variable directly as part of the path parameter in the JSON_VALUE() call, but you may try one of the following approaches:
Concatenate the #counter variable in the path parameter (SQL Server 2017 is needed).
Parse the JSON with OPENJSON() and the appropriate WHERE clause.
JSON:
DECLARE #counter INT = 0;
DECLARE #pjson nvarchar(max) = N'{
"store":{
"storeId":100,
"name":"TEST",
"lastUpdatedBy":"MULE",
"location":{
"addresses":[
{
"addressType":"MAIN",
"name":"Name1",
"name2":"Name2",
"address":"Address1",
"address2":"Address2",
"city":"City",
"lastUpdateBy":"MULE"
},
{
"addressType":"SECONDARY",
"name":"Name1",
"name2":"Name2",
"address":"Address1",
"address2":"Address2",
"city":"City",
"lastUpdateBy":"MULE"
},
{
"addressType":"BILLING",
"name":"Name1",
"name2":"Name2",
"address":"Address1",
"address2":"Address2",
"city":"City",
"lastUpdateBy":"MULE"
}
]
}
}
}'
Statement with variable concatenation:
SELECT JSON_VALUE(
#pjson,
CONCAT(N'lax $.store.location.addresses[', #counter, N'].addressType')
)
Statement with OPENJSON():
SELECT JSON_VALUE([value], '$.addressType')
FROM OPENJSON(#pjson, 'lax $.store.location.addresses')
WHERE CONVERT(int, [key]) = #counter
Result:
(No column name)
----------------
MAIN

Answer 2

Try following:
DECLARE #pJson NVARCHAR(4000)
-- ...
DECLARE #Counter INT = 0
DECLARE #PathString NVARCHAR(1000)
SET #PathString = N'lax $.store.location.addresses[' + CAST(#Counter AS NVARCHAR(50)) + N'].addressType'
PRINT JSON_VALUE(#Pjson,#PathString)