User_Defined_Function/udf_parseJSON.sql

CREATE FUNCTION dbo.udf_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,/* 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,/* each list or object has an object id. This ties all elements to a parent. Lists are treated as objects here */

   NAME NVARCHAR(2000),/* 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

   

 

  DECLARE @Strings TABLE /* 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 */

    (

     String_ID INT IDENTITY(1, 1),

     StringValue NVARCHAR(MAX)

    )

  SELECT--initialise the characters to convert hex to ascii

    @characters='0123456789abcdefghijklmnopqrstuvwxyz',

    @SequenceNo=0, --set the sequence no. to something sensible.

  /* firstly we process all strings. This is done because [{} and ] aren't escaped in strings, which complicates an iterative parse. */

    @parent_ID=0;

  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 --no end delimiter to last string

        BREAK --no more

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

      --now put in the escaped control characters

      SELECT @token=REPLACE(@token, FROMString, TOString)

      FROM

        (SELECT

          '\"' AS FromString, '"' AS ToString

         UNION ALL SELECT '\\', '\'

         UNION ALL SELECT '\/', '/'

         UNION ALL 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)

        ) substitutions

      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(NVARCHAR(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(NVARCHAR(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=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

        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

GO