TSQL JSON How to add an array to an existing Json Object? - json

Question

We've got a SQL query where we create a JSON file with for JSON Path.
We want to merge 2 JSON objects into 1 JSON. But we struggle with the code how to accomplish this task.
We tried JSON_MODIFY to merge them together using append. But this did not work for us.
What we'd like to do is this, we have 2 seperate json objects and we want to merge them as one.
Json Object A:
{
"ID" : 0,
"Name" : "a name",
"Description" : "a description"
}
and Json Object B
"Nodes" : [
{
"NodeID" : 10,
"NodeName" : "Node 0"
},
{
"NodeID" : 11,
"NodeName" : "Node 1"
}
]
What we want to have:
{
"ID" : 0,
"Name" : "a name",
"Description" : "a description",
"Nodes" : [
{
"NodeID" : 10,
"NodeName" : "Node 0"
},
{
"NodeID" : 11,
"NodeName" : "Node 1"
}
]
}
Our current SQL Query looks like this:
set #JsonCourse = ( select c.name, c.id, c.description from dbo.courses c where c.id = #id for json path)
set #JsonNodes = ( select n.id, n.name from dbo.nodes n where n.courseId = #id for json path, root('Nodes'))
set #CompleteJson = JSON_MODIFY(#JsonCourse,'append $',JSON_QUERY(#JsonNodes));
print #CompleteJson
But our result is like this:
[
{
"ID" : 0,
"Name" : "a name",
"Description" : "a description"
},
{
"Nodes" : [
{
"NodeID" : 10,
"NodeName" : "Node 0"
},
{
"NodeID" : 11,
"NodeName" : "Node 1"
}
]
}
]
Note: we've used hypothetical data here.
How do we fix this with JSON_MODIFY?

Answer 1

So I'll add another answer, as this is a completely different thing as the first answer:
As I do not have your tables, I'll set the JSON variables to the values you provided
DECLARE #json1 NVARCHAR(MAX)=
N'{
"ID" : 0,
"Name" : "a name",
"Description" : "a description"
}'
DECLARE #json2 NVARCHAR(MAX)= --<-- had to add the surrounding {}, otherwise this was invalid JSON
N'{"Nodes" :
[
{
"NodeID" : 10,
"NodeName" : "Node 0"
},
{
"NodeID" : 11,
"NodeName" : "Node 1"
}
]}';
--We do not need append here.
--We have to tell the engine the name of the new node.
--To avoid repeated key Nodes I read from the #json2 using $.Nodes as path
DECLARE #CompleteJSON NVARCHAR(MAX)=JSON_MODIFY(#Json1,'$.Nodes',JSON_QUERY(#Json2,'$.Nodes'));
PRINT #CompleteJSON;
I hope this is closer to your needs...

Answer 2

Please read about creating a MCVE. This is a stand-alone sample, which makes your issue reproducible, and helps us to provide easy answers...
If I got this correctly there is a 1:n related structure, where each node in your "object A" can have several nodes in "object B".
My following code will simulate this through INFORMATION_SCHEMA. Each table as 1 or many columns.
We solve this with a correlated sub-query. This is the way to create nested JSON arrays:
SELECT TOP 3 t.TABLE_NAME AS NodeName
,t.TABLE_TYPE AS NodeType
,(
SELECT TOP 3 c.COLUMN_NAME AS ColumnName
,c.DATA_TYPE AS ColumnType
FROM INFORMATION_SCHEMA.COLUMNS c
WHERE c.TABLE_CATALOG=t.TABLE_CATALOG
AND c.TABLE_SCHEMA=t.TABLE_SCHEMA
AND c.TABLE_NAME=t.TABLE_NAME
FOR JSON PATH
) AS MyColumns
FROM INFORMATION_SCHEMA.TABLES t
FOR JSON PATH;
The result
[
{
"NodeName": "spt_fallback_db",
"NodeType": "BASE TABLE",
"MyColumns": [
{
"ColumnName": "xserver_name",
"ColumnType": "varchar"
},
{
"ColumnName": "xdttm_ins",
"ColumnType": "datetime"
},
{
"ColumnName": "xdttm_last_ins_upd",
"ColumnType": "datetime"
}
]
},
{
"NodeName": "spt_fallback_dev",
"NodeType": "BASE TABLE",
"MyColumns": [
{
"ColumnName": "xserver_name",
"ColumnType": "varchar"
},
{
"ColumnName": "xdttm_ins",
"ColumnType": "datetime"
},
{
"ColumnName": "xdttm_last_ins_upd",
"ColumnType": "datetime"
}
]
},
{
"NodeName": "spt_fallback_usg",
"NodeType": "BASE TABLE",
"MyColumns": [
{
"ColumnName": "xserver_name",
"ColumnType": "varchar"
},
{
"ColumnName": "xdttm_ins",
"ColumnType": "datetime"
},
{
"ColumnName": "xdttm_last_ins_upd",
"ColumnType": "datetime"
}
]
}
]
As you can see, each table as a nested set of columns, represented through a JSON array.