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How to manipulate JSON data in SQL server?

Manipulate JSON data in SQL Server

JavaScript Object Notation (JSON) is a lightweight popular data exchangeable format used across modern IoT platforms, web and mobile applications etc. It is a language independent textual data format. JavaScript Object Notation (JSON) is also used for storing unstructured data in log files or NoSQL Databases such as Microsoft Azure Cosmos DB. Many RESTful web services that allow us to store and retrieve JSON formatted texts among different protocols using different Endpoints. The example of JSON text is as follows,
[{
        "customer":"Michael",
        "products":["Watch","Mobile","Books"]
},
{
        "customer":"Stuart",
        "products":["Laptop","Keyboard","Mouse"]
}]
In this article you will understand the following,

  • Read JSON data from table
  • Modify JSON data in a table
  • Validate JSON objects 
  • Convert array of JSON objects into table format

Lets see how to retrieve JSON data from a table?

Read JSON data from table

Here we are using JSON_VALUE predefined function to retrieve column values from JSON objects.
In this example, we are using country wise sales table to read customer and product list details.
SELECT Country, 
 JSON_VALUE(Data,'$.Customers.customer') AS Customer,
 JSON_VALUE(Data,'$.Customers.products') AS Products
FROM tbl_CountryWiseSales
The JSON_VALUE function used to extract an object or an array from a JSON string instead of a scalar value. In lax mode JSON_VALUE returns null, In strict mode JSON_VALUE returns an exception.










The JSON_VALUE function returns null when there is an nested array of objects like you can see in the above example, we are having customer array objects in this we are having nested multiple products list, when you see the return result you can see the NULL products because the JSON_VALUE function returns null when there is nested objects. In order to read this value we need to use JSON_QUERY function instead.
SELECT Country, 
JSON_VALUE(Data,'$.Customers.customer') AS Customer,
JSON_QUERY(Data,'$.Customers.products') AS Products
FROM tbl_CountryWiseSales
The JSON_QUERY is used to extract a scalar value from a JSON string instead of an object or an array.

Modify JSON data in a table

The JSON_MODIFY function is used to update the values of a property in JSON string and return the updated JSON string. The following example illustrates how to update a value of a property in a variable that contains JSON?.
update tbl_CountryWiseSales set Data=JSON_MODIFY(Data,'$.Customers.customer','Michael Raj')
where JSON_VALUE(Data,'$.Customers.customer')='Michael';
The updated JSON data should be like this,
In order to update the nested object values, your query should be like this,
update tbl_CountryWiseSales set Data=JSON_MODIFY(Data,'$.Customers.products[0]','Watch1')
where JSON_VALUE(Data,'$.Customers.customer')='Michael Raj';
The query returned result is,

Validate JSON data 

In order to validate JSON data we are using ISJSON() straightforward built-in function. The ISJSON() tests whether a string contains valid JSON or not. The following example returns rows in which the column "Data" contains valid JSON.
SELECT Country,Data
FROM tbl_CountryWiseSales
where ISJSON(Data)>0;
The returned result is,


Convert JSON objects into table format

The OPENJSON function is used to easily convert JSON data to rows and colmns. The OPENJSON provides a row set view over a JSON document. You can explicitly specify the columns in the row set and the JSON property paths used to populate the columns. With OPENJSON function you can easily import JSON files into SQL server or convert JSON data into table format. The following example returns a nested objects by specifying the path:
SELECT [Key],value
FROM tbl_CountryWiseSales  
CROSS APPLY OPENJSON (Data,'$.Customers.products') as p 
The returned result is,
By without specifying path, your query should be like this:
SELECT [Key],value
FROM tbl_CountryWiseSales  
CROSS APPLY OPENJSON (Data)
 The result is,
Suppose, If you want to read the top level object values the query should be:
SELECT Country,v.customer
FROM tbl_CountryWiseSales  
CROSS APPLY OPENJSON (Data) WITH (customer nvarchar(100) '$.Customers.customer') as v
The returned result is,
The OPENJSON uses key value pair to retrieve JSON data as well as it removes duplicate property values.



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