SQL Server FOR JSON PATH, Exclude specific field if null - sql

Question

I have table with data like this
Id | Name | Phone | OtherField
----+---------+--------+-----------
1 | ABC | 12344 | NULL
2 | XYZ | NULL | NULL
I want a SQL query to transform it like this
[
{
"ID":1,
"Name":"ABC",
"Phone":[
{"Home":"12344"}
],
"OtherFields":NULL
},
{
"ID":1,
"Name":"ABC",
"OtherFields":NULL
}
]
I know about INCLUDE_NULL_VALUES it includes all the empty field.
I want to include all other fields except Phone.

Answer 1

I have edited my answer as you have changed your original request.
I don't believe you can have it both ways, keeping some NULLs and not others. The best way I can think of at the moment is to use ISNULL on columns you must keep.
For example:
DECLARE #Table TABLE ( Id INT, Name VARCHAR(10), Phone VARCHAR(10), OtherField VARCHAR(10) );
INSERT INTO #Table ( Id, Name, Phone ) VALUES
( 1, 'ABC', '12344' ), ( 2, 'XYZ', NULL );
SELECT
Id, Name,
JSON_QUERY ( CASE
WHEN t.Phone IS NOT NULL THEN x.Phone
ELSE NULL
END ) AS Phone,
ISNULL( OtherField, '' ) AS OtherFields
FROM #Table t
CROSS APPLY (
SELECT ( SELECT Phone AS Home FOR JSON PATH ) AS Phone
) x
FOR JSON PATH;
Returns
[{
"Id": 1,
"Name": "ABC",
"Phone": [{
"Home": "12344"
}],
"OtherFields": ""
}, {
"Id": 2,
"Name": "XYZ",
"OtherFields": ""
}]

Answer 2

Update:
The original question was edited and I don't think that you can generate the expected ouptut using a single FOR JSON and INCLUDE_NULL_VALUES, because now the table has more than one column with NULL values (OtherField in the example).
As a possible solution you may try a mixed approach (using FOR JSON and STRING_AGG()) to build the final JSON output and keep the NULL values for all columns, except Phones:
CREATE TABLE Data (
Id int,
Name varchar(100),
Phone varchar(100),
OtherField varchar(1)
);
INSERT INTO Data (Id, Name, Phone, OtherField)
VALUES
(1, 'ABC', '12344', NULL),
(2, 'ABC', NULL, NULL),
(3, 'ABC', NULL, NULL)
Statement:
SELECT CONCAT(
'[',
(
SELECT STRING_AGG(j.Json, ',')
FROM Data d
CROSS APPLY (
SELECT CASE
WHEN Phone IS NOT NULL THEN (
SELECT Id, Name, (SELECT Phone AS Home FOR JSON PATH) AS Phone, OtherField
FOR JSON PATH, INCLUDE_NULL_VALUES, WITHOUT_ARRAY_WRAPPER
)
ELSE (
SELECT Id, Name, OtherField
FOR JSON PATH, INCLUDE_NULL_VALUES, WITHOUT_ARRAY_WRAPPER
)
END
) j (Json)
),
']'
)
Result:
[
{"Id":1,"Name":"ABC","Phone":[{"Home":"12344"}],"OtherField":null},
{"Id":2,"Name":"ABC","OtherField":null},
{"Id":3,"Name":"ABC","OtherField":null}
]
Original answer:
You may try the following statement:
Table:
CREATE TABLE Data (
Id int,
Name varchar(100),
Phone varchar(100)
);
INSERT INTO Data (Id, Name, Phone)
VALUES
(1, 'ABC', '12344'),
(2, 'ABC', NULL )
Statement:
SELECT
Id,
Name,
JSON_QUERY(CASE WHEN Phone IS NOT NULL THEN (SELECT Phone AS Home FOR JSON PATH) END) AS Phone
FROM Data
FOR JSON PATH
Result:
[
{"Id":1,"Name":"ABC","Phone":[{"Home":"12344"}]},
{"Id":2,"Name":"ABC"}
]