MS SQL Query a field containing JSON - json

Question

I have the following JSON in a SQL field in a table:
{
"type": "info",
"date": "2019/11/12 14:28:51",
"state": {
"6ee8587f-3b8c-4e5c-89a9-9f04752607f0": {
"state": "open",
"color": "#0000ff"
}
},
...
}
I query this in MS SQL using the folloing:
SELECT
JSON_VALUE(json_data, '$.type') AS msg_type
,JSON_VALUE(json_data, '$."date"') AS event_date
,JSON_QUERY(json_data, '$.state."6ee8587f-3b8c-4e5c-89a9-9f04752607f0".state') AS json_state
,JSON_QUERY(json_data, '$.state."6ee8587f-3b8c-4e5c-89a9-9f04752607f0".color') AS json_color
FROM
[dbo].[tbl_json_dump]
To get the date (a reserved word) back I have to put the the field name in like $."date"
I cannot seem to get the data back for the state or color fields and I think it has to do with that it is nested under "6ee8587f-3b8c-4e5c-89a9-9f04752607f0" because when I query :
JSON_QUERY(json_data, '$.state."6ee8587f-3b8c-4e5c-89a9-9f04752607f0"') AS json_state
I get the object back -
{"state":"open","color":"#0000ff"}
but using
JSON_QUERY(json_data, '$.state."6ee8587f-3b8c-4e5c-89a9-9f04752607f0".state') AS json_state
it is not working
Any suggestions on what I'm doing wrong??

Answer 1

Just replace JSON_QUERY with JSON_VALUE since you're interested in getting the value.
JSON_QUERY is supposed to return a JSON fragment and designed to work on objects and arrays, not values.

Answer 2

Salman A already provided the answer. Just to add a few points.
JSON_VALUE() - Extracts a Scalar value
JSON_QUERY() - Extracts an object or an array from a JSON string.
If you see the syntax , JSON_QUERY ( expression [ , path ] ) & JSON_VALUE ( expression , path ) , both are more or less except the [] square brackets for path and it means optional. It is because JSON_QUERY() can extract whole JSON field if required.
And on the return types,
JSON_VALUE() returns a JSON fragment of type nvarchar(max)
JSON_QUERY() returns a single text value of type nvarchar(4000)
Overall comparison
DECLARE #data NVARCHAR(4000)
SET #data=N'{
"type": "info",
"date": "2019/11/12 14:28:51",
"state": {
"6ee8587f-3b8c-4e5c-89a9-9f04752607f0": {
"state": "open",
"color": "#0000ff"
}
},
}'
SELECT
JSON_VALUE(#data,'$.state."6ee8587f-3b8c-4e5c-89a9-9f04752607f0"') AS 'JSON_VALUE_FAILED',
JSON_QUERY(#data,'$.state."6ee8587f-3b8c-4e5c-89a9-9f04752607f0"') AS 'JSON_QUERY_SUCCEED',
JSON_VALUE(#data,'$.state."6ee8587f-3b8c-4e5c-89a9-9f04752607f0".state') AS 'JSON_VALUE_SUCCEED',
JSON_QUERY(#data,'$.state."6ee8587f-3b8c-4e5c-89a9-9f04752607f0".state') AS 'JSON_QUERY_SUCCEED';
Check Output here

Answer 3

You may try with another possible approach (more complicated), which parses all nested JSON objects.
Table:
CREATE TABLE Data (
JsonData nvarchar(max)
)
INSERT INTO Data
(JsonData)
VALUES
(N'{
"type": "info",
"date": "2019/11/12 14:28:51",
"state": {
"6ee8587f-3b8c-4e5c-89a9-9f04752607f0": {
"state": "open",
"color": "#0000ff"
},
"6ee8587f-3b8c-4e5c-89a9-9f04752607f1": {
"state": "open",
"color": "#0000ff"
}
}
}')
Statement:
SELECT
j1.[type], j1.[date], j2.[key], j3.state, j3.color
FROM Data d
CROSS APPLY OPENJSON(d.JsonData) WITH (
[type] nvarchar(100) '$.type',
[date] datetime '$.date',
[state] nvarchar(max) '$.state' AS JSON
) j1
CROSS APPLY OPENJSON(j1.state) j2
CROSS APPLY OPENJSON(j2.[value]) WITH (
state nvarchar(10) '$.state',
color nvarchar(10) '$.color'
) j3
Result:
type date key state color
info 12/11/2019 14:28:51 6ee8587f-3b8c-4e5c-89a9-9f04752607f0 open #0000ff
info 12/11/2019 14:28:51 6ee8587f-3b8c-4e5c-89a9-9f04752607f1 open #0000ff
Notes:
If the input JSON has only one key "6ee8587f-3b8c-4e5c-89a9-9f04752607f0" in the "state" JSON object, you may get the value with JSON_VALUE() using the correct path $.state."6ee8587f-3b8c-4e5c-89a9-9f04752607f0".state.