Flatten nested JSON data into SQL Server tables - json

Question

I have a JSON file that contains transactions, and each transaction contains multiple items. I need to flatten the data into SQL Server tables using T-SQL.
I have tried different options to flatten it, but it looks like I am missing something. Anyone who has worked on a similar structure have any ideas how this could be accomplished? 
DECLARE #json NVARCHAR(MAX);
SELECT #json = JsonPath
FROM [dbo].[stg_transactionsJson] b;
SELECT
CONVERT(NVARCHAR(50), JSON_VALUE(c.Value, '$.orderId')) AS orderId,
CONVERT(DATETIME, JSON_VALUE(c.Value, '$.openTime')) AS openTime,
CONVERT(DATETIME, JSON_VALUE(c.Value, '$.closeTime')) AS closeTime,
CONVERT(NVARCHAR(50), JSON_VALUE(c.Value, '$.operatorId')) AS operatorId,
CONVERT(NVARCHAR(50), JSON_VALUE(c.Value, '$.terminalId')) AS terminalId,
CONVERT(NVARCHAR(50), JSON_VALUE(c.Value, '$.sessionId')) AS sessionId,
CONVERT(NVARCHAR(50), JSON_VALUE(p.Value, '$.productGroupId')) AS productGroupId,
CONVERT(NVARCHAR(150), JSON_VALUE(p.Value, '$.productId')) AS productId,
CONVERT(NVARCHAR(50), JSON_VALUE(p.Value, '$.quantity')) AS quantity,
CONVERT(NVARCHAR(150), JSON_VALUE(p.Value, '$.taxValue')) AS taxValue,
CONVERT(NVARCHAR(50), JSON_VALUE(p.Value, '$.value')) AS ProductValue,
CONVERT(NVARCHAR(150), JSON_VALUE(p.Value, '$.priceBandId')) AS priceBandId,
GETDATE() AS DateUpdated
FROM
OPENJSON(#json) AS c
OUTER APPLY
OPENJSON(c.Value, '$."products"') AS p;
And the sample JSON as follows
{
"orderId": 431,
"openTime": "2022-10-31T13:12:28",
"closeTime": "2022-10-31T13:12:32",
"operatorId": 7,
"terminalId": 4,
"sessionId": 1,
"products": [
{
"productId": 2632,
"productGroupId": 162,
"quantity": 1,
"taxValue": 0.58,
"value": 3.5,
"priceBandId": 2
},
{
"productId": 3224,
"productGroupId": 164,
"quantity": 1,
"taxValue": 0.08,
"value": 0.5,
"priceBandId": 2
}
],
"tenders": [
{
"tenderId": 2,
"value": 4.0
}
],
"type": 1,
"memberId": 1
}

Answer 1

You can Do it like this
First declare the values in an with clause and then cross apply the products
DECLARE #json NVARCHAR(MAX);
SET #json = '{
"orderId": 431,
"openTime": "2022-10-31T13:12:28",
"closeTime": "2022-10-31T13:12:32",
"operatorId": 7,
"terminalId": 4,
"sessionId": 1,
"products": [
{
"productId": 2632,
"productGroupId": 162,
"quantity": 1,
"taxValue": 0.58,
"value": 3.5,
"priceBandId": 2
},
{
"productId": 3224,
"productGroupId": 164,
"quantity": 1,
"taxValue": 0.08,
"value": 0.5,
"priceBandId": 2
}
],
"tenders": [
{
"tenderId": 2,
"value": 4.0
}
],
"type": 1,
"memberId": 1
}
';
SELECT c.orderId
,c.openTime
,c.closeTime
,c.operatorId
,c.terminalId
,c.sessionId
, JSON_VALUE(p.Value, '$.productGroupId') productGroupId
, JSON_VALUE(p.Value, '$.productId') productId
, JSON_VALUE(p.Value, '$.quantity') quantity
, JSON_VALUE(p.Value, '$.taxValue') taxValue
, JSON_VALUE(p.Value, '$.value') value
, JSON_VALUE(p.Value, '$.priceBandId') priceBandId
,GETDATE() AS DateUpdated
FROM
OPENJSON(#json) WITH (
orderId int '$.orderId',
openTime date '$.openTime',
closeTime date '$.closeTime',
operatorId int '$.operatorId',
terminalId int '$.terminalId',
sessionId int '$.sessionId',
[products] NVARCHAR(MAX) as JSON) c
CROSS APPLY OPENJSON(c.products) p
orderId
openTime
closeTime
operatorId
terminalId
sessionId
productGroupId
productId
quantity
taxValue
value
priceBandId
DateUpdated
431
2022-10-31
2022-10-31
7
4
1
162
2632
1
0.58
3.5
2
2023-01-11 13:57:47.607
431
2022-10-31
2022-10-31
7
4
1
164
3224
1
0.08
0.5
2
2023-01-11 13:57:47.607
fiddle

Answer 2

The expected output defines the exact statement, but if you need to parse nested JSON content you may try a combination of:
OPENJSON() with explicit schema and the AS JSON modifier for nested JSON
additional APPLY operators for each nested level.
T-SQL:
SELECT
j1.orderId, j1.openTime, j1.closeTime, j1.operatorId, j1.terminalId, j1.sessionId, j1.type, j1.memberId,
j2.productGroupId, j2.productId, j2.quantity, j2.taxValue, j2.productValue, j2.priceBandId,
j3.tenderId, j3.tenderValue
FROM stg_transactionsJson s
OUTER APPLY OPENJSON(s.stg_transactionsJson) WITH (
orderId NVARCHAR(50) '$.orderId',
openTime DATETIME '$.openTime',
closeTime DATETIME '$.closeTime',
operatorId NVARCHAR(50) '$.operatorId',
terminalId NVARCHAR(50) '$.terminalId',
sessionId NVARCHAR(50) '$.sessionId',
products NVARCHAR(MAX) '$.products' AS JSON,
tenders NVARCHAR(MAX) '$.tenders' AS JSON,
type int '$.type',
memberId int '$.memberId'
) j1
OUTER APPLY OPENJSON(j1.products) WITH (
productGroupId NVARCHAR(50) '$.productGroupId',
productId NVARCHAR(150) '$.productId',
quantity NVARCHAR(50) '$.quantity',
taxValue NVARCHAR(150) '$.taxValue',
productValue NVARCHAR(50) '$.value',
priceBandId NVARCHAR(150)'$.priceBandId'
) j2
OUTER APPLY OPENJSON(j1.tenders) WITH (
tenderId NVARCHAR(150) '$.tenderId',
tenderValue NVARCHAR(50) '$.value'
) j3