SQL to JSON - How to get query output without column names then put together the two columns

Question

For example, a table called User has columns FirstName and LastName. So when I query

SELECT * FROM User FOR JSON PATH

The output is

[{ "FirstName": "Bruce",
   "LastName": "Wayne"
}]

But the output I am trying to get is

[{ "Bruce" : "Wayne" }]

Answer 1

In JSON, the structure is "Property" : "Value". You are attempting to create a JSON with the structure "Value" : "Value".
I'm not sure why you would want such a thing or even if it's a good idea, but to get to this you can create the output string yourself as gotqn suggested in his comment instead of using FOR JSON.

First, create and populate sample table (Please save us this step in your future questions):

CREATE TABLE [user]
(
    FirstName varchar(10),
    LastName varchar(10)
)

INSERT INTO [User] (FirstName, LastName) VALUES 
('Bruce', 'Wayne'),
('Clark', 'Kent'),
('Peter', 'Parker'),
('Tony', 'Stark')

The query:

SELECT STUFF(
    (
    SELECT ',{"'+ FirstName +'" : "'+ LastName +'"}' 
    FROM [User]
    FOR XML PATH('')
    )
, 1, 1, '[') + ']' As JsonOutput

Results:

JsonOutput
[{"Bruce" : "Wayne"},{"Clark" : "Kent"},{"Peter" : "Parker"},{"Tony" : "Stark"}]