SQL Select with JSON Column and Group By [duplicate] - sql

Question

SQL 2016 has a new feature which converts data on SQL server to JSON. I am having difficulty in combining array of objects into array of values i.e.,
EXAMPLE -
CREATE TABLE #temp (item_id VARCHAR(256))
INSERT INTO #temp VALUES ('1234'),('5678'),('7890')
SELECT * FROM #temp
--convert to JSON
SELECT (SELECT item_id
FROM #temp
FOR JSON PATH,root('ids'))
RESULT -
{
"ids": [{
"item_id": "1234"
},
{
"item_id": "5678"
},
{
"item_id": "7890"
}]
}
But I want the result as -
"ids": [
"1234",
"5678",
"7890"
]
Can somebody please help me out?

Answer 1

Thanks! The soultion we found is converting into XML first -
SELECT
JSON_QUERY('[' + STUFF(( SELECT ',' + '"' + item_id + '"'
FROM #temp FOR XML PATH('')),1,1,'') + ']' ) ids
FOR JSON PATH , WITHOUT_ARRAY_WRAPPER

Answer 2

Martin!
I believe this is an even simpler way of doing it:
SELECT '"ids": ' +
REPLACE(
REPLACE( (SELECT item_id FROM #temp FOR JSON AUTO),'{"item_id":','' ),
'"}','"' )

Answer 3

declare #temp table (item_id VARCHAR(256))
INSERT INTO #temp VALUES ('1234'),('5678'),('7890')
SELECT * FROM #temp
--convert to JSON
select
json_query(QUOTENAME(STRING_AGG('"' + STRING_ESCAPE(item_id, 'json') + '"', char(44)))) as [json]
from #temp
for json path
When we want to concatenate strings as json array then:
escape string - STRING_ESCAPE
concatenate string with comma separator - STRING_AGG, comma ascii code is 44
add quotation it in brackets - QUOTENAME (without param)
return string (with array of elements) as json - JSON_QUERY

Answer 4

Since arrays of primitive values are valid JSON, it seems strange that a facility for selecting arrays of primitive values isn't built into SQL Server's JSON functionality. (If on the contrary such functionality exists, I at least haven't been able to discover it after quite a bit of searching).
The approach outlined above works as described. But when applied for a field in a larger query, the array of primitives is surrounded with quotes.
E.g., this
DECLARE #BomTable TABLE (ChildNumber dbo.udt_ConMetPartNumber);
INSERT INTO #BomTable (ChildNumber) VALUES (N'101026'), (N'101027');
SELECT N'"Children": ' + REPLACE(REPLACE((SELECT ChildNumber FROM #BomTable FOR JSON PATH), N'{"ChildNumber":', N''), '"}','');
works by producing:
"Children": ["101026,"101027]
But, following the approach above, this:
SELECT
p.PartNumber,
p.Description,
REPLACE(REPLACE((SELECT
ChildNumber
FROM
Part.BillOfMaterials
WHERE
ParentNumber = p.PartNumber
ORDER BY
ChildNumber
FOR
JSON AUTO
), N'{"ChildNumber":', N''), '"}', '"') AS [Children]
FROM
Part.Parts AS p
WHERE
p.PartNumber = N'104444'
FOR
JSON PATH
Produces:
[
{
"PartNumber": "104444",
"Description": "ASSY HUB R-SER DRIV HP10 ABS",
"Children": "[\"101026\",\"101027\",\"102291\",\"103430\",\"103705\",\"104103\"]"
}
]
Where the Children array is wrapped as a string.

Answer 5

This version (building on the others):
correctly escapes an special JSON characters (e.g. quotes)
returns an empty array [] for no data
Requires SQL 2017 or later (due to STRING_AGG):
SELECT
CONCAT('[',
(SELECT STRING_AGG('"' + STRING_ESCAPE(item_id, 'json') + '"', ',')
FROM #temp)
, ']')

Answer 6

Here's a wild idea that may or may not be practical. Recurse over your data set and append things to your JSON arrays using JSON_MODIFY:
with
d (d) as (select * from (values (1),(2),(3),(4)) t (d)),
j (d, j) as (
-- Adapt the recursion to make it dynamic
select 1, json_modify('[]', 'append $', d)
from d
where d = 1
union all
select d.d, json_modify(j, 'append $', d.d)
from d join j on d.d = j.d + 1
)
select *
from j;
I kept it simple for illustration purposes. You'll adapt it to make it dynamic, of course. This produces:
|d |j |
|---|---------|
|1 |[1] |
|2 |[1,2] |
|3 |[1,2,3] |
|4 |[1,2,3,4]|
Could even be used to emulate standard SQL JSON_ARRAYAGG

Answer 7

Most of these solutions are essentially creating a CSV that represents the array contents, and then putting that CSV into the final JSON format. Here's what I use, to avoid XML:
DECLARE #tmp NVARCHAR(MAX) = ''
SELECT #tmp = #tmp + '"' + [item_id] + '",'
FROM #temp -- Defined and populated in the original question
SELECT [ids] = JSON_QUERY((
SELECT CASE
WHEN #tmp IS NULL THEN '[]'
ELSE '[' + SUBSTRING(#tmp, 0, LEN(#tmp)) + ']'
END
))
FOR JSON PATH, WITHOUT_ARRAY_WRAPPER