Query JSON with SQL!

Taken directly from simple-talk.com; read more to see an excellent way to convert your stored SQL stored JSON string into a results table

You won’t benefit from indexing with this query (as you can in XML) but it will allow you to query JSON directly at the point of storage (one for the SQL developers than the web developers I guess!)

The function!

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(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

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