Joseph Michael Pesch
VP Programming

SQL Table Valued Function to Parse JSON

by 18. May 2017 11:58

 

 

CREATE FUNCTION [dbo].[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(500),--either a string or object -- slayne 7/10/14: increased from 200 to 500
    @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

Tags:

SQL Server