XML and JSON making simple changes

As part of the XML and JSON month of blog posts, this post is going to cover how to make changes to XML and JSON in TSQL.We will be using the same sample data from the original post with a data structure holding employee data.

CREATE TABLE XmlAndJson
(
	id INTEGER IDENTITY NOT NULL,
	XmlData XML,
    JsonData NVARCHAR(MAX)
);
GO
ALTER TABLE XmlAndJson
  ADD CONSTRAINT [JsonData record should be formatted as JSON]
  CHECK (ISJSON(JsonData)=1);

GO
SET NOCOUNT ON;
DECLARE @XmlData as XML;
set @XmlData = '<employees>
  <employee>
    <firstName>Steve</firstName>
	<lastName>Stedman</lastName>
  </employee>
  <employee>
    <firstName>Derrick</firstName>
	<lastName>Bovenkamp</lastName>
  </employee>
  <employee>
    <firstName>Bill</firstName>
	<lastName>Simpkins</lastName>
  </employee>
</employees>';

DECLARE @JsonData as VARCHAR(MAX);
set @JsonData = '
{"employees":[
  { "firstName":"Steve", "lastName":"Stedman" },
  { "firstName":"Derrick", "lastName":"Bovenkamp" },
  { "firstName":"Bill", "lastName":"Simpkins" }
]}';

INSERT INTO XmlAndJson(XmlData, JsonData)
VALUES (@XmlData, @JsonData );

Since we are just past the 4th of July (Independence Day in the US), we will attempt to make a change in the first employee listed to replace Steve Stedman with Ben Franklin, one of the founding fathers and early presidents of the United States. If you are in another country and you are feeling patriotic, feel free to replace Ben Franklin with your own local historic figure.

To start with, lets first take a look at the data we are going to be changing:

 -- modifying data, first check the row we are going to change.
 SELECT JSON_VALUE(JsonData, '$.employees[0].firstName') as FirstName,
        JSON_VALUE(JsonData, '$.employees[0].lastName') as LastName,
		*
  FROM XmlAndJson
  WHERE ID = 1;

SELECT XmlData.value('(/employees/employee/firstName)[1]', 'varchar(max)') as FirstName,
	   XmlData.value('(/employees/employee/lastName)[1]', 'varchar(max)') as LastName,
	   *
  FROM XmlAndJson
  WHERE ID = 1;

We are going to do 4 things in this demo for both xml and json. Change the first name of the first entry to be Ben, the last name for that entry to Franklin, add a age of 341, and a hobby of kites. Yes Ben was a fan of flying kites. For each of these we are going to pull the data value out of the table, make several changes, then update it in the table. We could use an update statement to modify things every step of the way if that was needed.

Modifying JSON

--JSON_MODIFY
DECLARE @json as NVARCHAR(MAX);

SELECT @json = JsonData
  FROM XmlAndJson
 WHERE ID = 1;

-- change firstname
SET @json = JSON_MODIFY(@json, '$.employees[0].firstName', 'Ben') ;

-- change lastname
SET @json = JSON_MODIFY(@json, '$.employees[0].lastName', 'Franklin') ;

-- add age 
SET @json = JSON_MODIFY(@json, '$.employees[0].age', '314') ;

-- add hobby
SET @json = JSON_MODIFY(@json, '$.employees[0].hobby', 'Kites') ;

SELECT @json;

UPDATE XmlAndJson
   SET JsonData = @json
 WHERE ID = 1;

Once complete we will check our results.

SELECT JSON_VALUE(JsonData, '$.employees[0].firstName') as FirstName,
       JSON_VALUE(JsonData, '$.employees[0].lastName') as LastName,
       JSON_VALUE(JsonData, '$.employees[0].age') as Age,
       JSON_VALUE(JsonData, '$.employees[0].hobby') as Hobby,
	   *
  FROM XmlAndJson
 WHERE ID = 1;

The JSON_MODIFY function was used to both change the existing values as well as to add new values.

Modifying XML

Modifying XML is a tiny bit more complex in that there are different options for updating an existing value versus inserting a new value. It is a slightly different syntax.

--XML Modify
DECLARE @xml as XML;

SELECT @xml = XmlData
  FROM XmlAndJson
 WHERE ID = 1;

 
-- change firstname
SET @xml.modify('replace value of (/employees/employee/firstName/text())[1] with "Ben"');

-- change lastname
SET @xml.modify('replace value of (/employees/employee/lastName/text())[1] with "Franklin"');

-- add age 
SET @xml.modify('insert <age>314</age> into (/employees/employee)[1]');

-- add hobby
SET @xml.modify('insert <hobby>Kites</hobby> into (/employees/employee)[1]');

SELECT @xml;

UPDATE XmlAndJson
   SET XmlData = @xml
 WHERE ID = 1;

Then we check our changes:

 SELECT XmlData.value('(/employees/employee/firstName)[1]', 'varchar(max)') as FirstName,
		XmlData.value('(/employees/employee/lastName)[1]', 'varchar(max)') as LastName,
		XmlData.value('(/employees/employee/age)[1]', 'varchar(max)') as Age,
		XmlData.value('(/employees/employee/hobby)[1]', 'varchar(max)') as Hobby,
		*
  FROM XmlAndJson
  WHERE ID = 1;

Summary

You can see with either XML or JSON it is easy to make simple updates and changes to the data in either format. Perhaps the most complex part was figuring out the syntax to insert and update the XML values. Hopefully these examples will help with that.

XML and JSON making simple changes

Modifying JSON

Modifying XML

Summary

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