SQL Server - How to transform JSON to Relational database - sql

Question

How can we use SQL to Convert a JSON statement into different tables?
For example we have JSON:
{"table1":
{"Name":"table1","Items":
[{"Id":1,"FirstName":"John",
"LastName":"Wen","Country":"UK",
"PostCode":1234,"Status":false,
"Date":"2018-09-18T08:30:32.91",}]},
"table2":
{"Name":"table2","Items":
[{"Id":1,"Name":"leo",
"StudentId":102,"CreatedDate":"2018-09-18","Location":"USA"}]}}
In the relational database, we will get two tables once the JSON is converted
For example, schema 'Table1':
Id FirstName LastName Country PostCode Status Date
1 John Wen UK 1234 false 2018-09-18T08:30:32.91
And the 'Table2' will look like:
Id Name StudentId CreateDate Location
1 Leo 102 2018-9-18 USA
Could anyone please give any advices on it.

Answer 1

You can do this using openjson and json_value functions. Try the following:
Declare #json nvarchar(max),#table1Items nvarchar(max), #table2Items nvarchar(max)
set #json='{
"table1": {
"Name": "table1",
"Items": [{
"Id": 1,
"FirstName": "John",
"LastName": "Wen",
"Country": "UK",
"PostCode": 1234,
"Status": false,
"Date": "2018-09-18T08:30:32.91"
}, {
"Id": 2,
"FirstName": "John1",
"LastName": "Wen1",
"Country": "UK1",
"PostCode": 12341,
"Status": true,
"Date": "2018-09-15T08:30:32.91"
}]
},
"table2": {
"Name": "table2",
"Items": [{
"Id": 1,
"Name": "leo",
"StudentId": 102,
"CreatedDate": "2018-09-18",
"Location": "USA"
}]
}
}'
set #table1Items=(select value from OpenJSON((select value from OpenJSON(#Json) where [key]='table1')) where [key]='Items')
set #table2Items=(select value from OpenJSON((select value from OpenJSON(#Json) where [key]='table2')) where [key]='Items')
--select for table 1
select JSON_VALUE(val,'$.Id') as ID,
JSON_VALUE(val,'$.FirstName') as FirstName,
JSON_VALUE(val,'$.LastName') as LastName,
JSON_VALUE(val,'$.Country') as Country,
JSON_VALUE(val,'$.PostCode') as PostCode,
JSON_VALUE(val,'$.Status') as Status,
JSON_VALUE(val,'$.Date') as Date
from
(
select value as val from openJSON(#table1Items)
) AS Table1JSON
--select for table 1
select JSON_VALUE(val,'$.Id') as ID,
JSON_VALUE(val,'$.Name') as FirstName,
JSON_VALUE(val,'$.StudentId') as LastName,
JSON_VALUE(val,'$.CreatedDate') as Country,
JSON_VALUE(val,'$.Location') as PostCode
from
(
select value as val from openJSON(#table2Items)
) AS Table2JSON
It is working exactly as you wanted. At the end, the two select statements return the tables as you mentioned. Just add them to your desired table using insert into select. I have also tried adding another object to table1 array and verified that it is working fine i.e. returning two rows for two objects. Hope this helps

Answer 2

If SQL Version 2016+ use OPENJSON AND with_clause:
https://learn.microsoft.com/en-us/sql/t-sql/functions/openjson-transact-sql?view=sql-server-2017
DECLARE #JsonData NVARCHAR(MAX);
SET #JsonData = N'
{
"table1": {
"Name": "table1",
"Items": [
{
"Id": 1,
"FirstName": "John",
"LastName": "Wen",
"Country": "UK",
"PostCode": 1234,
"Status": false,
"Date": "2018-09-18T08:30:32.91"
},
{
"Id": 2,
"FirstName": "John1",
"LastName": "Wen1",
"Country": "UK1",
"PostCode": 12341,
"Status": true,
"Date": "2018-09-15T08:30:32.91"
}
]
},
"table2": {
"Name": "table2",
"Items": [
{
"Id": 1,
"Name": "leo",
"StudentId": 102,
"CreatedDate": "2018-09-18",
"Location": "USA"
}
]
}
}
';
--Table1
SELECT [a].[Id]
, [a].[FistName]
, [a].[Lastname]
, [a].[Country]
, [a].[PostCode]
, [a].[Status]
, [a].[Date]
FROM
OPENJSON(#JsonData, '$.table1.Items')
WITH (
[Id] INT '$.Id'
, [FistName] NVARCHAR(200) '$.FirstName'
, [Lastname] NVARCHAR(200) '$.LastName'
, [Country] NVARCHAR(200) '$.Country'
, [PostCode] NVARCHAR(200) '$.PostCode'
, [Status] NVARCHAR(200) '$.Status'
, [Date] DATETIME '$.Date'
) [a];
--Table2
SELECT [a].[Id]
, [a].[Name]
, [a].[StudentId]
, [a].[CreatedDate]
, [a].[Location]
FROM
OPENJSON(#JsonData, '$.table2.Items')
WITH (
[Id] INT '$.Id'
, [Name] NVARCHAR(200) '$.Name'
, [StudentId] INT '$.StudentId'
, [CreatedDate] DATETIME '$.CreatedDate'
, [Location] NVARCHAR(200) '$.Location'
) [a];

Answer 3

Try using OPENJSON function in SQL Server:
ReferenceLink_1
ReferenceLink_2