SQL with Manoj

In my previous posts I talked about how to [export] a Table or Query data into JSON string format, and [read it back] from JSON string to Relational-table format, and with [nested elements].
 

Here, in this post I’ll show how we can store JSON data in a normal table column, just like you store XML data.

XML data is stored in a column of XML datatype which also check the validity of the XML data to be stored. But to store JSON data there is no new datatype introduced, JSON can be stored in an NVARCHAR datatype column just like a plain text, and to validate it you can add a CHECK constraint on it.

IsJSON() function: can be used as a CHECK constraint on the columns that contain JSON string which will validate if the JSON string is in proper format or not.
 

As we will need AdvantureWorks2014 Sample Database in our example below, we need to upgrade its Compatibility from SQL 2014 to SQL 2016, i.e. from level 120 to 130, like:

USE [master]
GO

ALTER DATABASE [AdventureWorks2014] SET COMPATIBILITY_LEVEL = 130
GO

You can download AdvantureWorks2014 sample Database from Microsoft [CodePlex site].
 

–> Ok, now let’s create a new Table with OrderDetailsJSON column for storing JSON string with a CHECK constraint on it:

USE [AdventureWorks2014]
GO

CREATE TABLE CustomerOrder (
	BusinessEntityID INT, 
	FirstName NVARCHAR(50), 
	MiddleName NVARCHAR(50), 
	LastName NVARCHAR(50), 
	EmailPromotion INT,

	OrderDetailsJSON NVARCHAR(MAX) -- normal column with NVARCHAR datatype
		CHECK ( IsJSON ( OrderDetailsJSON ) = 1 ) -- CHECK Constraint to validate JSON string
)

–> Let’s create a sample record-set with JSON data in OrderDetailsJSON column. We will use FOR JSON AUTO option to convert relational data to JSON string for our example, as shown below:

;WITH CTE_PersonContact AS (
	SELECT 
		BusinessEntityID, FirstName, MiddleName, LastName, EmailPromotion,
		OrderDetailsJSON = 
		(	SELECT SalesOrderID, OrderDate, SubTotal, TaxAmt, TotalDue
			FROM [AdventureWorks2014].[Sales].[SalesOrderHeader] S
			WHERE S.CustomerID = P.BusinessEntityID
			FOR JSON AUTO -- here
		) -- our JSON column
	FROM [Person].[Person] P
)
INSERT INTO CustomerOrder
SELECT 
	BusinessEntityID, FirstName, MiddleName, LastName, EmailPromotion, 
	OrderDetailsJSON
FROM CTE_PersonContact
WHERE OrderDetailsJSON IS NOT NULL

-- (9778 row(s) affected)

–> Check the above inserted records with the OrderDetailsJSON column containing data in JSON format:

SELECT * FROM CustomerOrder

-- (9778 row(s) affected)

–> Let’s Query back the JSON data from the OrderDetailsJSON column with other columns in relational form, by using OPENJSON() function. As for each Customer it can contain multiple orders we will get multiple rows for each Customer and multiple columns as per defined in the JSON string:

SELECT 
	C.BusinessEntityID, C.FirstName, C.MiddleName, C.LastName, C.EmailPromotion, 
	J.SalesOrderID, J.OrderDate, J.SubTotal, J.TaxAmt, J.TotalDue
FROM CustomerOrder C
CROSS APPLY OPENJSON (OrderDetailsJSON)
WITH (
	SalesOrderID INT, 
	OrderDate DATETIME, 
	SubTotal MONEY, 
	TaxAmt MONEY, 
	TotalDue MONEY
) AS J

-- (17463 row(s) affected)

–> And if you want to get just one Order per Customer then you can use following Query, by using JSON_Value() function and by specifying the array key pointer/position to get the first value fro the array:

SELECT 
	C.BusinessEntityID, C.FirstName, C.MiddleName, C.LastName, C.EmailPromotion, 
	SalesOrderID		= JSON_Value (OrderDetailsJSON, '$[0].SalesOrderID'),
	OrderDate			= JSON_Value (OrderDetailsJSON, '$[0].OrderDate'),
	SubTotal			= JSON_Value (OrderDetailsJSON, '$[0].SubTotal'),
	TaxAmt				= JSON_Value (OrderDetailsJSON, '$[0].TaxAmt'),
	TotalDue			= JSON_Value (OrderDetailsJSON, '$[0].TotalDue')
FROM CustomerOrder C

-- (9778 row(s) affected)

We can also use JSON string for passing multiple values from a single parameter in an Stored Procedure to implement dynamic parameters functionality as a workaround, check the [blog post] for the same.