SQL Server : JSON formatting grouping possible? - arrays

Question

I have a single SQL Server table of the form:
192.168.1.1, 80 , tcp
192.168.1.1, 443, tcp
...
I am exporting this to json like this:
SELECT
hostIp AS 'host.ip',
'ports' = (SELECT port AS 'port', protocol AS 'protocol'
FOR JSON PATH)
FROM
test
FOR JSON PATH
This query results in:
[
{
"host": {
"ip": "192.168.1.1"
},
"ports": [
{
"port": 80,
"protocol": "tcp"
}
]
},
{
"host": {
"ip": "192.168.1.1"
},
"ports": [
{
"port": 443,
"protocol": "tcp"
}
]
},
....
However I wanted all data from a single IP grouped as such:
[
{
"host": {
"ip": "192.168.1.1"
},
"ports": [
{
"port": 80,
"protocol": "tcp"
},
{
"port": 443,
"protocol": "tcp"
}
]
},
...
I have found that there seems to be aggregate functions, but they either don't work for me or are for Postgresql, my example is in SQL Server.
Any idea how to get this to work?

Answer 1

The only simple way to do this is to self-join
SELECT
tOuter.hostIp AS [host.ip]
,ports = (
SELECT
tInner.port
,tInner.protocol
FROM test tInner
FOR JSON PATH
)
FROM test tOuter
GROUP BY
tOuter.hostIp
FOR JSON PATH;
It is obviously inefficient to self-join, but SQL Server does not support JSON_AGG. You can simulate it with STRING_AGG and no self-join
SELECT
t.hostIp AS [host.ip]
,ports = JSON_QUERY('[' + STRING_AGG(tInner.json, ',') + ']')
FROM test t
CROSS APPLY (
SELECT
t.port
,t.protocol
FOR JSON PATH, WITHOUT_ARRAY_WRAPPER
) tInner(json)
GROUP BY
t.hostIp
FOR JSON PATH;
db<>fiddle
As you might imagine, it gets more complex as more and more levels of nesting are involved.
Note:
Do not use ' for quoting column names, only []
There is no need to alias a column for JSON if it is already that name