JSON Vs. XML! The wrong choice can influence the success or the fail of your project!

SQL Server Performance: JSON vs XML – Which One Is Faster?

SQL Server Performance Series – JSON vs XML

Hi SQL Server Guys,

In performance discussions, usually a very important question came up:

Should we use JSON or XML in SQL Server?

At first glance this may look like a simple design decision.

But in real production systems the choice between JSON and XML can have a significant impact on performance, scalability, and maintainability.

In many projects, choosing the wrong format can introduce unnecessary overhead and slow down critical queries.

In other words, the decision between JSON and XML can directly influence the success of the system we are building.

That is exactly why this comparison is so important.

Let’s look at what happens when we compare JSON and XML in SQL Server.

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JSON vs XML Performance Test

By doing internal tests comparing JSON and XML processing, the results i got were quite interesting.

When parsing and retrieving values from structured payloads:

• Small dataset (10 rows): JSON was about 9x faster
• Larger dataset (1000 rows): JSON was about 7x faster

In addition to speed improvements, JSON payloads were also significantly smaller.

In the test scenario, JSON data was roughly 40–50% smaller than the equivalent XML representation.

Smaller payloads mean less network traffic and less parsing overhead inside SQL Server.

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Example: Extracting Data from JSON

Read values from JSON is very straightforward.

DECLARE @json NVARCHAR(MAX) =
'{
   "CustomerID": 101,
   "OrderTotal": 250,
   "City": "London"
}'

SELECT 
    JSON_VALUE(@json, '$.CustomerID') AS CustomerID,
    JSON_VALUE(@json, '$.OrderTotal') AS OrderTotal,
    JSON_VALUE(@json, '$.City') AS City

JSON_VALUE is lightweight and optimized for fast parsing of simple values.

This often results in very fast execution times.

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Example: Extracting Data from XML

Let's perform the same operation using XML.

DECLARE @xml XML =
'
<Order>
    <CustomerID>101</CustomerID>
    <OrderTotal>250</OrderTotal>
    <City>London</City>
</Order>
'

SELECT
    @xml.value('(/Order/CustomerID)[1]', 'INT') AS CustomerID,
    @xml.value('(/Order/OrderTotal)[1]', 'INT') AS OrderTotal,
    @xml.value('(/Order/City)[1]', 'VARCHAR(50)') AS City

XML parsing uses XQuery expressions. They are are more powerful but also heavier to process.

This additional complexity is one of the reasons XML processing can be slower.

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Another Example: Parsing Arrays

SQL Server also provides OPENJSON for parsing arrays efficiently.

DECLARE @json NVARCHAR(MAX) =
'[
 {"CustomerID":1,"Total":100},
 {"CustomerID":2,"Total":200},
 {"CustomerID":3,"Total":300}
]'

SELECT *
FROM OPENJSON(@json)
WITH (
    CustomerID INT,
    Total INT
)

This function allows SQL Server to convert JSON arrays directly into relational rows.

For many modern workloads, this is extremely efficient.

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So, when XML Still Makes Sense

Despite JSON's performance advantages, XML still has valid use cases.

Using XML may be preferable when:

• strict schema validation is required
• complex hierarchical documents are needed
• existing integrations already rely on XML
• legacy enterprise systems expect XML formats

Many enterprise systems still rely heavily on XML-based integrations.

In those environments, performance might not be the only factor to consider.

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Recommended Reading

If you want to learn another classic SQL Server performance mistake, check out my previous article:

Why SELECT * Is Still Killing SQL Server Performance in 2026

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The Real Lesson

Both JSON and XML are powerful data formats supported by SQL Server.

But when performance, simplicity, and scalability are important, JSON often provides clear advantages.

In many modern SQL Server workloads, JSON parsing tends to be faster and produces smaller payloads.

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And remember…

No SQL Server was harmed while parsing JSON & XML 😉

See you in the next SQL Server performance deep dive!

Luca Biondi @ 2026