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Posts Tagged ‘JSON_Value’

Store JSON data in a table, OPENJSON and JSON_Value functions | SQL Server 2016 – Part 4

November 2, 2015 2 comments

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)

SQL Server 2016 - JSON table
 

–> 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)

SQL Server 2016 - JSON table 2
 

–> 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.


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Reading JSON string with Nested elements | SQL Server 2016 – Part 3

November 1, 2015 5 comments

In my [previous post] I discussed about how to Import or Read a JSON string and convert it in relational/tabular format in row/column from.

Today in this post I’ll talk about how to read/parse JSON string with nested elements, just like XML.
 

Native JSON support in SQL Server 2016 provides you few functions to read and parse your JSON string into relational format and these are:

– OPENJSON() Table valued function: parses JSON text and returns rowset view of JSON.

– JSON_Value() Scalar function: returns a value from JSON on the specified path.

We will see usage of both the functions in our example below:
 

Here, we have just one nested element, and the OPENJSON() function will get you the child elements values.

–> Method #1.a. Using OPENJSON() function:

DECLARE @json NVARCHAR(1000)
SELECT @json = 
N'{
  "OrderHeader": [
    {
      "OrderID": 100,
      "CustomerID": 2000,

      "OrderDetail": 
        {
          "ProductID": 2000, 
		  "UnitPrice": 350 		
		}
    }
  ]
}'

SELECT 
	OrderID, 
	CustomerID, 
	
	[OrderDetail.ProductID] AS ProductID, 
	[OrderDetail.UnitPrice] AS UnitPrice 

FROM OPENJSON (@json, '$.OrderHeader') 
WITH (
	OrderID INT, 
	CustomerID INT, 

	[OrderDetail.ProductID] INT, 
	[OrderDetail.UnitPrice] INT
) AS Orders 
OrderID	CustomerID	ProductID	UnitPrice
100	2000		2000		350

 

But, if you have more than one nested elements the same query will give just 1 row with NULL values under the child columns, like this.

–> Method #1.b. In case of multiple child elements:

DECLARE @json NVARCHAR(1000)
SELECT @json = 
N'{
  "OrderHeader": [
    {
      "OrderID": 100,
      "CustomerID": 2000,

      "OrderDetail": [
        {
          "ProductID": 2000, 
		  "UnitPrice": 350 		
		}, 		
		{ 		      
		  "ProductID": 3000,
          "UnitPrice": 450
        }
      ]
    }
  ]
}'

SELECT 
	OrderID, 
	CustomerID, 
	
	[OrderDetail.ProductID] AS ProductID, 
	[OrderDetail.UnitPrice] AS UnitPrice 

FROM OPENJSON (@json, '$.OrderHeader') 
WITH (
	OrderID INT, 
	CustomerID INT, 

	[OrderDetail.ProductID] INT, 
	[OrderDetail.UnitPrice] INT
) AS Orders 
OrderID	CustomerID	ProductID	UnitPrice
100	2000		NULL		NULL

You might be expecting 2 rows with same OrderID & CustomerID, with different ProductID & UnitPrice, right?

Instead you get ProductID & UnitPrice column values as NULL. Because, here you are having array of child elements with OrderDetail node (notice the square-bracket after “OrderDetail”: node), thus the Query is not able to find the key on the path.
 

In this case what you have to do is, use the array positions with square brackets (“[” and “]”) in your query and call out separate columns for each child element, like below:

DECLARE @json NVARCHAR(1000)
SELECT @json = 
N'{
  "OrderHeader": [
    {
      "OrderID": 100,
      "CustomerID": 2000,

      "OrderDetail": [
        {
          "ProductID": 2000, 
		  "UnitPrice": 350 		
		}, 		
		{ 		      
		  "ProductID": 3000,
          "UnitPrice": 450
        }
      ]
    }
  ]
}'

SELECT 
	OrderID, 
	CustomerID, 

	[OrderDetail[0]].ProductID] AS ProductID1, 
	[OrderDetail[0]].UnitPrice] AS UnitPrice1, 

	[OrderDetail[1]].ProductID] AS ProductID2, 
	[OrderDetail[1]].UnitPrice] AS UnitPrice2 

FROM OPENJSON (@json, '$.OrderHeader') 
WITH (
	OrderID INT, 
	CustomerID INT, 

	[OrderDetail[0]].ProductID] INT, 
	[OrderDetail[0]].UnitPrice] INT, 

	[OrderDetail[1]].ProductID] INT, 
	[OrderDetail[1]].UnitPrice] INT 
) AS Orders
OrderID	CustomerID	ProductID1	UnitPrice1	ProductID2	UnitPrice2
100	2000		2000		350		3000		450

 

You can also specify the child elements with full path by using the dollar sign “$” inside the WITH() clause (instead at column level above), like below:

–> Method #2. Using OPENJSON() function:

DECLARE @json NVARCHAR(1000)
SELECT @json = 
N'{
  "OrderHeader": [
    {
      "OrderID": 100,
      "CustomerID": 2000,

      "OrderDetail": [
        {
          "ProductID": 2000, 
		  "UnitPrice": 350 		
		}, 		
		{ 		      
		  "ProductID": 3000,
          "UnitPrice": 450
        }
      ]
    }
  ]
}'

SELECT 
	OrderID, 
	CustomerID, 

	ProductID1, 
	UnitPrice1, 

	ProductID2, 
	UnitPrice2

FROM OPENJSON (@json, '$.OrderHeader')
WITH (
	OrderID    INT '$.OrderID',
	CustomerID INT '$.CustomerID',

	ProductID1 INT '$.OrderDetail[0].ProductID',
	UnitPrice1 INT '$.OrderDetail[0].UnitPrice', 

	ProductID2 INT '$.OrderDetail[1].ProductID',
	UnitPrice2 INT '$.OrderDetail[1].UnitPrice' 
) AS Orders
OrderID	CustomerID	ProductID1	UnitPrice1	ProductID2	UnitPrice2
100	2000		2000		350		3000		450

Ok, so by using the key path and the array position we can get the child elements value in our Query result-set by using above 2 methods.
 

But instead of having them in separate columns how about pulling them in separate rows, this will also make your query dynamic as you would not know the number of child-elements before hand, right?

This can be done by CROSS APPLYing the JSON child node with the parent node and using the JSON_Value() function, like shown below:

–> Method #3. Using JSON_Value() with OPENJSON() function:

DECLARE @json NVARCHAR(1000)
SELECT @json = 
N'{
  "OrderHeader": [
    {
      "OrderID": 100,
      "CustomerID": 2000,

      "OrderDetail": [
        {
          "ProductID": 2000, 
		  "UnitPrice": 350 		
		}, 		
		{ 		      
		  "ProductID": 3000,
          "UnitPrice": 450
        },
		{ 		      
		  "ProductID": 4000,
          "UnitPrice": 550
        }
      ]
    }
  ]
}'

SELECT 
	JSON_Value (c.value, '$.OrderID') as OrderID, 
	JSON_Value (c.value, '$.CustomerID') as CustomerID, 
	JSON_Value (p.value, '$.ProductID') as ProductID, 
	JSON_Value (p.value, '$.UnitPrice') as UnitPrice

FROM OPENJSON (@json, '$.OrderHeader') as c
CROSS APPLY OPENJSON (c.value, '$.OrderDetail') as p
OrderID	CustomerID	ProductID	UnitPrice
100	2000		2000		350
100	2000		3000		450
100	2000		4000		550

 

Ok, that’s it for today.

In my [next post] I’ll talk about storing JSON string in a table and doing some hands-on with it.