SQL function to remove duplicate entries from a JSON array. Based on MYSQL 5.7+

json_uniq.sql

CREATE FUNCTION JSON_UNIQ(arr JSON) RETURNS json
BEGIN

	SET @arr = arr;
	SET @a_length = JSON_LENGTH(@arr);
	SET @loop_index = @a_length;

	WHILE @loop_index >= 0 DO

		SET @item = JSON_UNQUOTE(JSON_EXTRACT(@arr, concat('$[',@loop_index,']')));   
		SET @itemcount = coalesce(JSON_LENGTH(JSON_SEARCH(@arr, 'all', @item)), 0);

		IF @itemcount > 1 THEN
			SET @arr = JSON_REMOVE(@arr, CONCAT('$[',@loop_index,']'));
			SET @loop_index = @loop_index - 1;
		END IF;

		SET @loop_index = @loop_index - 1;

	End WHILE;

	RETURN CAST(@arr AS JSON);
    
END