ADF Data Flow flatten JSON to rows - json

Question

IN ADF Data Flow how can I flatten JSON into rows rather than columns?
{
"header": [
{
"main": {
"id": 1
},
"sub": [
{
"type": "a",
"id": 2
},
{
"type": "b",
"id": 3
}
]}]}
In ADF I'm using the flatten task and get the below result:
However the result I'm trying to achieve is merging the two id columns into one column like below:

Answer 1

Since both main_id and sub_id belong in the same column, instead of using 1 flatten to flatten all the data, flatten both main and sub separately.
I have taken the following JSON as source for my dataflow.
{
"header":[
{
"main":{
"id":1
},
"sub":[
{
"type":"a",
"id":2
},
{
"type":"b",
"id":3
}
]
},
{
"main":{
"id":4
},
"sub":[
{
"type":"c",
"id":5
},
{
"type":"d",
"id":6
}
]
}
]
}
I have taken 2 flatten transformations flattenMain and flattenSub instead of 1 which use the same source.
For flattenMain, I have unrolled by header and selected unroll root as header. Then created an additional column selecting source column header.main.id.
The data preview for flattenMain would be:
For flattenSub, I have unrolled by header.sub and selected unroll root as header.sub. Then created 2 additional column selecting source column header.sub.id as id column and header.sub.type as type column.
The data preview for flattenSub transformation would be:
Now I have applied union transformation on both flattenMain and flattenSub. I have applied union by using Name.
The final data preview for this Union transformation will give the desired result.
NOTE: All the highlighted rows in output images indicate the result that would be achieved when we use the JSON sample provided in the question.