рабочий фрагмент чтения узлов дерева(чисто для иллюстрации синтаксиса)
CREATE PROCEDURE FUNCTIONAL_SCAN(ENTERPRISE_ID INTEGER, ID INTEGER, DOWN SMALLINT, START_LEVEL SMALLINT, START_ORDER INTEGER)
RETURNS (NODE_ID INTEGER, NODE_LEVEL INTEGER, NODE_ORDER INTEGER)
AS
  DECLARE VARIABLE RIGHT_ID INTEGER;
  DECLARE VARIABLE TEMP_ID  INTEGER;
  
  BEGIN
    NODE_ID = ID;
    NODE_ORDER = START_ORDER;
    IF (DOWN = - 1 ) THEN
      BEGIN
        NODE_ID = NULL;
        SELECT ID
          FROM FUNCTIONAL
          WHERE (PARENT_ID = - 1 )
            AND (UPPER_ID = - 1 )
            AND (ENTERPRISE_ID = :ENTERPRISE_ID)
          INTO :NODE_ID;
        DOWN =  1 ;
      END
    NODE_LEVEL = START_LEVEL;
    WHILE (NODE_ID <> - 1 ) DO
      BEGIN
        SUSPEND;
        SELECT LOWER_ID, RIGHT_ID
          FROM FUNCTIONAL
          WHERE ID = :NODE_ID
          INTO :NODE_ID, :RIGHT_ID;
        IF (RIGHT_ID <> - 1 ) THEN
          BEGIN
            TEMP_ID = NODE_ID;
            FOR 
              SELECT NODE_ID, NODE_LEVEL, NODE_ORDER
                FROM FUNCTIONAL_SCAN(:ENTERPRISE_ID, :RIGHT_ID,   1 , :START_LEVEL+ 1 , :NODE_ORDER+ 1 )
                INTO :NODE_ID, :NODE_LEVEL, :NODE_ORDER
            DO
              SUSPEND;
            NODE_ID = TEMP_ID;
            NODE_LEVEL = START_LEVEL;
          END
        NODE_ORDER = NODE_ORDER+ 1 ;
        IF (DOWN =  0 ) THEN
          NODE_ID = - 1 ;
      END
    EXIT;
  END^