SQL Server 2019

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CREATE TABLE JSONBODY(Brand nvarchar(100), Engine nvarchar(100), Location nvarchar(100), Colour nvarchar(100), Interior nvarchar(100))
INSERT JSONBODY VALUES('Ford','V6','Boston','Blue','Black')
1 rows affected

SELECT (
SELECT
  v.fieldName,
  value = JSON_QUERY('[' + STRING_AGG('"' + STRING_ESCAPE(v.value, 'json') + '"', ',') + ']')
FROM [dbo].[JSONBODY] jb
CROSS APPLY (VALUES
    ('Brand',    jb.Brand),
    ('Engine',   jb.Engine),
    ('Location', jb.Location)
) v(fieldName, value)
WHERE v.value IS NOT NULL
GROUP BY
  v.fieldName
FOR JSON PATH, ROOT('fields')
)

UNION ALL

SELECT (
SELECT
  v.fieldName,
  [value.name] = JSON_QUERY('[[' + STRING_AGG('"' + STRING_ESCAPE(v.value, 'json') + '"', ',') + ']]')
FROM [dbo].[JSONBODY] jb
CROSS APPLY (VALUES
    ('Colour',   jb.Colour),
    ('Interior', jb.Interior)
) v(fieldName, value)
WHERE v.value IS NOT NULL
GROUP BY
  v.fieldName
FOR JSON PATH, ROOT('categories')
);


(No column name)


{"fields":[{"fieldName":"Brand","value":["Ford"]},{"fieldName":"Engine","value":["V6"]},{"fieldName":"Location","value":["Boston"]}]}

{"categories":[{"fieldName":"Colour","value":{"name":[["Blue"]]}},{"fieldName":"Interior","value":{"name":[["Black"]]}}]}


SELECT (
SELECT
  v.fieldName,
  value = JSON_QUERY('["' + STRING_ESCAPE(v.value, 'json') + '"]')
FROM [dbo].[JSONBODY] jb
CROSS APPLY (VALUES
    ('Brand',    jb.Brand),
    ('Engine',   jb.Engine),
    ('Location', jb.Location)
) v(fieldName, value)
WHERE v.value IS NOT NULL
FOR JSON PATH, ROOT('fields')
)

UNION ALL

SELECT (
SELECT
  v.fieldName,
  [value.name] = JSON_QUERY('[["' + STRING_ESCAPE(v.value, 'json') + '"]]')
FROM [dbo].[JSONBODY] jb
CROSS APPLY (VALUES
    ('Colour',   jb.Colour),
    ('Interior', jb.Interior)
) v(fieldName, value)
WHERE v.value IS NOT NULL
FOR JSON PATH, ROOT('categories')
);


(No column name)


{"fields":[{"fieldName":"Brand","value":["Ford"]},{"fieldName":"Engine","value":["V6"]},{"fieldName":"Location","value":["Boston"]}]}

{"categories":[{"fieldName":"Colour","value":{"name":[["Blue"]]}},{"fieldName":"Interior","value":{"name":[["Black"]]}}]}