Format query results as JSON with FOR JSON

Applies to: SQL Server 2016 (13.x) and later Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics (serverless SQL pool only)

Format query results as JSON, or export data from SQL Server as JSON, by adding the FOR JSON clause to a SELECT statement. Use the FOR JSON clause to simplify client applications by delegating the formatting of JSON output from the app to SQL Server.

Format query results

When you use the FOR JSON clause, you can specify the structure of the JSON output explicitly, or let the structure of the SELECT statement determine the output.

• To maintain full control over the format of the JSON output, use FOR JSON PATH. You can create wrapper objects and nest complex properties.

• To format the JSON output automatically based on the structure of the SELECT statement, use FOR JSON AUTO.

Here's an example of a SELECT statement with the FOR JSON clause and its output.

SELECT name, surname
FROM emp
FOR JSON AUTO;

[{
    "name": "John"
}, {
    "name": "Jane",
    "surname": "Doe"
}]

DROP TABLE IF EXISTS #tabStudent;
DROP TABLE IF EXISTS #tabClass;
GO

CREATE TABLE #tabClass (
    ClassGuid UNIQUEIDENTIFIER NOT NULL DEFAULT newid(),
    ClassName NVARCHAR(32) NOT NULL
);

CREATE TABLE #tabStudent (
    StudentGuid UNIQUEIDENTIFIER NOT NULL DEFAULT newid(),
    StudentName NVARCHAR(32) NOT NULL,
    ClassGuid UNIQUEIDENTIFIER NULL -- Foreign key.
);
GO

INSERT INTO #tabClass (ClassGuid, ClassName)
VALUES
    ('DE807673-ECFC-4850-930D-A86F921DE438', 'Algebra Math'),
    ('C55C6819-E744-4797-AC56-FF8A729A7F5C', 'Calculus Math'),
    ('98509D36-A2C8-4A65-A310-E744F5621C83', 'Art Painting');

INSERT INTO #tabStudent (StudentName, ClassGuid)
VALUES
    ('Alice Apple', 'DE807673-ECFC-4850-930D-A86F921DE438'),
    ('Alice Apple', 'C55C6819-E744-4797-AC56-FF8A729A7F5C'),
    ('Betty Boot', 'C55C6819-E744-4797-AC56-FF8A729A7F5C'),
    ('Betty Boot', '98509D36-A2C8-4A65-A310-E744F5621C83'),
    ('Carla Cap', null);
GO

SELECT c.ClassName,
    s.StudentName
FROM #tabClass AS c
RIGHT JOIN #tabStudent AS s ON s.ClassGuid = c.ClassGuid
ORDER BY c.ClassName,
    s.StudentName
FOR JSON AUTO
    -- To include NULL values in the output, uncomment the following line:
    --, INCLUDE_NULL_VALUES
    ;
GO

DROP TABLE IF EXISTS #tabStudent;
DROP TABLE IF EXISTS #tabClass;
GO

JSON_F52E2B61-18A1-11d1-B105-00805F49916B

[
   {"s":[{"StudentName":"Carla Cap"}]},
   {"ClassName":"Algebra Math","s":[{"StudentName":"Alice Apple"}]},
   {"ClassName":"Art Painting","s":[{"StudentName":"Betty Boot"}]},
   {"ClassName":"Calculus Math","s":[{"StudentName":"Alice Apple"},{"StudentName":"Betty Boot"}]}
]

Control other JSON output options

Control the output of the FOR JSON clause, using the following extra options.

• ROOT

  To add a single, top-level element to the JSON output, specify the ROOT option. If you don't specify this option, the JSON output doesn't have a root element. For more info, see Add a Root Node to JSON Output with the ROOT Option (SQL Server).

• INCLUDE_NULL_VALUES

  To include null values in the JSON output, specify the INCLUDE_NULL_VALUES option. If you don't specify this option, the output doesn't include JSON properties for NULL values in the query results. For more info, see Include Null Values in JSON - INCLUDE_NULL_VALUES Option.

• WITHOUT_ARRAY_WRAPPER

  To remove the square brackets that surround the JSON output of the FOR JSON clause by default, specify the WITHOUT_ARRAY_WRAPPER option. Use this option to generate a single JSON object as output from a single-row result. If you don't specify this option, the JSON output is formatted as an array - that is, the output is enclosed within square brackets. For more info, see Remove Square Brackets from JSON - WITHOUT_ARRAY_WRAPPER Option.

Output of the FOR JSON clause

The output of the FOR JSON clause has the following characteristics:

1. The result set contains a single column.

   • A small result set can contain a single row.
   • A large result set splits the long JSON string across multiple rows.

     • By default, SQL Server Management Studio (SSMS) concatenates the results into a single row when the output setting is Results to Grid. The SSMS status bar displays the actual row count.

     • Other client applications might require code to recombine lengthy results into a single, valid JSON string by concatenating the contents of multiple rows. For an example of this code in a C# application, see Use FOR JSON output in a C# client app.

       

2. The results are formatted as an array of JSON objects.

   • The number of elements in the JSON array is equal to the number of rows in the results of the SELECT statement (before the FOR JSON clause is applied).

   • Each row in the results of the SELECT statement (before the FOR JSON clause is applied) becomes a separate JSON object in the array.

   • Each column in the results of the SELECT statement (before the FOR JSON clause is applied) becomes a property of the JSON object.

3. Both the names of columns and their values are escaped according to JSON syntax. For more info, see How FOR JSON escapes special characters and control characters (SQL Server).

Example

Here's an example that demonstrates how the FOR JSON clause formats the JSON output.

Query results

JSON output

[{
    "A": 10,
    "B": 11,
    "C": 12,
    "D": "X"
}, {
    "A": 20,
    "B": 21,
    "C": 22,
    "D": "Y"
}, {
    "A": 30,
    "B": 31,
    "C": 32,
    "D": "Z"
}]

Related content

• How FOR JSON converts SQL Server data types to JSON data types (SQL Server)
• How FOR JSON escapes special characters and control characters (SQL Server)
• JSON as a bridge between NoSQL and relational worlds
• SELECT - FOR Clause (Transact-SQL)
• Use FOR JSON output in SQL Server and in client apps (SQL Server)