SET TERM !!!;
EXECUTE BLOCK AS
BEGIN
  IF(NOT(EXISTS(SELECT * 
                        FROM    RDB$RELATION_FIELDS A
                        WHERE  (A.RDB$RELATION_NAME = 'RECTPRICES')
                           AND   (A.RDB$FIELD_NAME = 'EDITDATE')
     )))THEN
  begin
    EXECUTE STATEMENT 
      'ALTER TABLE RECTPRICES
ADD EDITDATE DATE;';
  end
END!!!
SET TERM;!!!