Parse Json In Sql Server Below 2016

CREATE FUNCTION [Platform].[parseJSON] (@JSON NVARCHAR(MAX))
RETURNS @hierarchy TABLE (
	Element_ID INT IDENTITY(1, 1) NOT NULL /* internal surrogate primary key gives the order of parsing and the list order */
	,SequenceNo [int] NULL /* the place in the sequence for the element */
	,Parent_ID INT NULL /* if the element has a parent then it is in this column. The document is the ultimate parent, so you can get the structure from recursing from the document */
	,[Object_ID] INT NULL /* each list or object has an object id. This ties all elements to a parent. Lists are treated as objects here */
	,[Name] NVARCHAR(2000) NULL /* the Name of the object */
	,StringValue NVARCHAR(MAX) NOT NULL /*the string representation of the value of the element. */
	,ValueType VARCHAR(10) NOT NULL /* the declared type of the value represented as a string in StringValue*/
	)
AS
BEGIN
	DECLARE @FirstObject INT --the index of the first open bracket found in the JSON string
		,@OpenDelimiter INT --the index of the next open bracket found in the JSON string
		,@NextOpenDelimiter INT --the index of subsequent open bracket found in the JSON string
		,@NextCloseDelimiter INT --the index of subsequent close bracket found in the JSON string
		,@Type NVARCHAR(10) --whether it denotes an object or an array
		,@NextCloseDelimiterChar CHAR(1) --either a '}' or a ']'
		,@Contents NVARCHAR(MAX) --the unparsed contents of the bracketed expression
		,@Start INT --index of the start of the token that you are parsing
		,@end INT --index of the end of the token that you are parsing
		,@param INT --the parameter at the end of the next Object/Array token
		,@EndOfName INT --the index of the start of the parameter at end of Object/Array token
		,@token NVARCHAR(200) --either a string or object
		,@value NVARCHAR(MAX) -- the value as a string
		,@SequenceNo INT -- the sequence number within a list
		,@Name NVARCHAR(200) --the Name as a string
		,@Parent_ID INT --the next parent ID to allocate
		,@lenJSON INT --the current length of the JSON String
		,@characters NCHAR(36) --used to convert hex to decimal
		,@result BIGINT --the value of the hex symbol being parsed
		,@index SMALLINT --used for parsing the hex value
		,@Escape INT --the index of the next escape character
		/* in this temporary table we keep all strings, even the Names of the elements, since they are 'escaped' in a different way, and may contain, unescaped, brackets denoting objects or lists. These are replaced in the JSON string by tokens representing the string */
	DECLARE @Strings TABLE (
		String_ID INT IDENTITY(1, 1)
		,StringValue NVARCHAR(MAX)
		)

	IF ISNULL(@JSON, '') = ''
		RETURN

	SELECT @characters = '0123456789abcdefghijklmnopqrstuvwxyz' --initialise the characters to convert hex to ascii
		,@SequenceNo = 0 --set the sequence no. to something sensible.
		,@Parent_ID = 0;

	/* firstly we process all strings. This is done because [{} and ] aren't escaped in strings, which complicates an iterative parse. */
	WHILE 1 = 1 --forever until there is nothing more to do
	BEGIN
		SELECT @start = PATINDEX('%[^a-zA-Z]["]%', @json collate SQL_Latin1_General_CP850_Bin);--next delimited string

		IF @start = 0
			BREAK --no more so drop through the WHILE loop

		IF SUBSTRING(@json, @start + 1, 1) = '"'
		BEGIN --Delimited Name
			SET @start = @Start + 1;
			SET @end = PATINDEX('%[^\]["]%', RIGHT(@json, LEN(@json + '|') - @start) collate SQL_Latin1_General_CP850_Bin);
		END

		IF @end = 0 --either the end or no end delimiter to last string
		BEGIN -- check if ending with a double slash...
			SET @end = PATINDEX('%[\][\]["]%', RIGHT(@json, LEN(@json + '|') - @start) collate SQL_Latin1_General_CP850_Bin);

			IF @end = 0 --we really have reached the end 
			BEGIN
				BREAK --assume all tokens found
			END
		END

		SELECT @token = SUBSTRING(@json, @start + 1, @end - 1)

		--now put in the escaped control characters
		SELECT @token = REPLACE(@token, FromString, ToString)
		FROM (
			SELECT '\b'
				,CHAR(08)
			
			UNION ALL
			
			SELECT '\f'
				,CHAR(12)
			
			UNION ALL
			
			SELECT '\n'
				,CHAR(10)
			
			UNION ALL
			
			SELECT '\r'
				,CHAR(13)
			
			UNION ALL
			
			SELECT '\t'
				,CHAR(09)
			
			UNION ALL
			
			SELECT '\"'
				,'"'
			
			UNION ALL
			
			SELECT '\/'
				,'/'
			) substitutions(FromString, ToString)

		SELECT @token = Replace(@token, '\\', '\')

		SELECT @result = 0
			,@escape = 1

		--Begin to take out any hex escape codes
		WHILE @escape > 0
		BEGIN
			SELECT @index = 0 --find the next hex escape sequence
				,@escape = PATINDEX('%\x[0-9a-f][0-9a-f][0-9a-f][0-9a-f]%', @token collate SQL_Latin1_General_CP850_Bin)

			IF @escape > 0 --if there is one
			BEGIN
				WHILE @index < 4 --there are always four digits to a \x sequence   
				BEGIN
					SELECT --determine its value
						@result = @result + POWER(16, @index) * (CHARINDEX(SUBSTRING(@token, @escape + 2 + 3 - @index, 1), @characters) - 1)
						,@index = @index + 1;
				END

				-- and replace the hex sequence by its unicode value
				SELECT @token = STUFF(@token, @escape, 6, NCHAR(@result))
			END
		END

		--now store the string away 
		INSERT INTO @Strings (StringValue)
		SELECT @token

		-- and replace the string with a token
		SELECT @JSON = STUFF(@json, @start, @end + 1, '@string' + CONVERT(NCHAR(5), @@identity))
	END

	-- all strings are now removed. Now we find the first leaf.  
	WHILE 1 = 1 --forever until there is nothing more to do
	BEGIN
		SELECT @Parent_ID = @Parent_ID + 1

		--find the first object or list by looking for the open bracket
		SELECT @FirstObject = PATINDEX('%[{[[]%', @json collate SQL_Latin1_General_CP850_Bin) --object or array

		IF @FirstObject = 0
			BREAK

		IF (SUBSTRING(@json, @FirstObject, 1) = '{')
			SELECT @NextCloseDelimiterChar = '}'
				,@type = 'object'
		ELSE
			SELECT @NextCloseDelimiterChar = ']'
				,@type = 'array'

		SELECT @OpenDelimiter = @firstObject

		WHILE 1 = 1 --find the innermost object or list...
		BEGIN
			SELECT @lenJSON = LEN(@JSON + '|') - 1

			--find the matching close-delimiter proceeding after the open-delimiter
			SELECT @NextCloseDelimiter = CHARINDEX(@NextCloseDelimiterChar, @json, @OpenDelimiter + 1)

			--is there an intervening open-delimiter of either type
			SELECT @NextOpenDelimiter = PATINDEX('%[{[[]%', RIGHT(@json, @lenJSON - @OpenDelimiter) collate SQL_Latin1_General_CP850_Bin) --object

			IF @NextOpenDelimiter = 0
				BREAK

			SELECT @NextOpenDelimiter = @NextOpenDelimiter + @OpenDelimiter

			IF @NextCloseDelimiter < @NextOpenDelimiter
				BREAK

			IF SUBSTRING(@json, @NextOpenDelimiter, 1) = '{'
				SELECT @NextCloseDelimiterChar = '}'
					,@type = 'object'
			ELSE
				SELECT @NextCloseDelimiterChar = ']'
					,@type = 'array'

			SELECT @OpenDelimiter = @NextOpenDelimiter
		END

		---and parse out the list or Name/value pairs
		SELECT @contents = SUBSTRING(@json, @OpenDelimiter + 1, @NextCloseDelimiter - @OpenDelimiter - 1)

		SELECT @JSON = STUFF(@json, @OpenDelimiter, @NextCloseDelimiter - @OpenDelimiter + 1, '@' + @type + CONVERT(NCHAR(5), @Parent_ID))

		WHILE (PATINDEX('%[A-Za-z0-9@+.e]%', @contents collate SQL_Latin1_General_CP850_Bin)) <> 0
		BEGIN
			IF @Type = 'object' --it will be a 0-n list containing a string followed by a string, number,boolean, or null
			BEGIN
				SELECT @SequenceNo = 0
					,@end = CHARINDEX(':', ' ' + @contents) --if there is anything, it will be a string-based Name.

				SELECT @start = PATINDEX('%[^A-Za-z@][@]%', ' ' + @contents collate SQL_Latin1_General_CP850_Bin) --AAAAAAAA

				SELECT @token = RTrim(Substring(' ' + @contents, @start + 1, @End - @Start - 1))
					,@endofName = PATINDEX('%[0-9]%', @token collate SQL_Latin1_General_CP850_Bin)
					,@param = RIGHT(@token, LEN(@token) - @endofName + 1)

				SELECT @token = LEFT(@token, @endofName - 1)
					,@Contents = RIGHT(' ' + @contents, LEN(' ' + @contents + '|') - @end - 1)

				SELECT @Name = StringValue
				FROM @strings
				WHERE string_id = @param --fetch the Name
			END
			ELSE
				SELECT @Name = NULL
					,@SequenceNo = @SequenceNo + 1

			SELECT @end = CHARINDEX(',', @contents) -- a string-token, object-token, list-token, number,boolean, or null

			IF @end = 0
				--HR Engineering notation bugfix start
				IF ISNUMERIC(@contents) = 1
					SELECT @end = LEN(@contents) + 1
				ELSE
					--HR Engineering notation bugfix end 
					SELECT @end = PATINDEX('%[A-Za-z0-9@+.e][^A-Za-z0-9@+.e]%', @contents + ' ' collate SQL_Latin1_General_CP850_Bin) + 1

			SELECT @start = PATINDEX('%[^A-Za-z0-9@+.e][-A-Za-z0-9@+.e]%', ' ' + @contents collate SQL_Latin1_General_CP850_Bin)

			--select @start,@end, LEN(@contents+'|'), @contents  
			SELECT @Value = RTRIM(SUBSTRING(@contents, @start, @End - @Start))
				,@Contents = RIGHT(@contents + ' ', LEN(@contents + '|') - @end)

			IF SUBSTRING(@value, 1, 7) = '@object'
				INSERT INTO @hierarchy (
					[Name]
					,SequenceNo
					,Parent_ID
					,StringValue
					,[Object_ID]
					,ValueType
					)
				SELECT @Name
					,@SequenceNo
					,@Parent_ID
					,SUBSTRING(@value, 8, 5)
					,SUBSTRING(@value, 8, 5)
					,'object'
			ELSE IF SUBSTRING(@value, 1, 6) = '@array'
				INSERT INTO @hierarchy (
					[Name]
					,SequenceNo
					,Parent_ID
					,StringValue
					,[Object_ID]
					,ValueType
					)
				SELECT @Name
					,@SequenceNo
					,@Parent_ID
					,SUBSTRING(@value, 7, 5)
					,SUBSTRING(@value, 7, 5)
					,'array'
			ELSE IF SUBSTRING(@value, 1, 7) = '@string'
				INSERT INTO @hierarchy (
					[Name]
					,SequenceNo
					,Parent_ID
					,StringValue
					,ValueType
					)
				SELECT @Name
					,@SequenceNo
					,@Parent_ID
					,StringValue
					,'string'
				FROM @strings
				WHERE string_id = SUBSTRING(@value, 8, 5)
			ELSE IF @value IN ('true', 'false')
				INSERT INTO @hierarchy (
					[Name]
					,SequenceNo
					,Parent_ID
					,StringValue
					,ValueType
					)
				SELECT @Name
					,@SequenceNo
					,@Parent_ID
					,@value
					,'boolean'
			ELSE IF @value = 'null'
				INSERT INTO @hierarchy (
					[Name]
					,SequenceNo
					,Parent_ID
					,StringValue
					,ValueType
					)
				SELECT @Name
					,@SequenceNo
					,@Parent_ID
					,@value
					,'null'
			ELSE IF PATINDEX('%[^0-9-]%', @value collate SQL_Latin1_General_CP850_Bin) > 0
				INSERT INTO @hierarchy (
					[Name]
					,SequenceNo
					,Parent_ID
					,StringValue
					,ValueType
					)
				SELECT @Name
					,@SequenceNo
					,@Parent_ID
					,@value
					,'real'
			ELSE
				INSERT INTO @hierarchy (
					[Name]
					,SequenceNo
					,Parent_ID
					,StringValue
					,ValueType
					)
				SELECT @Name
					,@SequenceNo
					,@Parent_ID
					,@value
					,'int'

			IF @Contents = ' '
				SELECT @SequenceNo = 0
		END
	END

	INSERT INTO @hierarchy (
		[Name]
		,SequenceNo
		,Parent_ID
		,StringValue
		,[Object_ID]
		,ValueType
		)
	SELECT '-'
		,1
		,NULL
		,''
		,@Parent_ID - 1
		,@type

	RETURN
END