CREATE FUNCTION NEXT_DAY(DATE,CHAR)   RETURNS DATE AS ' DECLARE   ret DATE; BEGIN   IF $2 = ''日'' THEN       SELECT next_day($1,0) INTO ret;   END IF;   IF $2 = ''月'' THEN       SELECT next_day($1,1) INTO ret;   END IF;   IF $2 = ''火'' THEN       SELECT next_day($1,2) INTO ret;   END IF;   IF $2 = ''水'' THEN       SELECT next_day($1,3) INTO ret;   END IF;   IF $2 = ''木'' THEN       SELECT next_day($1,4) INTO ret;   END IF;   IF $2 = ''金'' THEN       SELECT next_day($1,5) INTO ret;   END IF;   IF $2 = ''土'' THEN       SELECT next_day($1,6) INTO ret;   END IF;   RETURN RET;  END;  ' LANGUAGE 'plpgsql'; CREATE FUNCTION NEXT_DAY(DATE,INT)   RETURNS DATE AS '  DECLARE    c ALIAS FOR $1;    p NUMERIC;    q ALIAS FOR $2;    ret DATE;  BEGIN   SELECT date_part(''dow'', c ) INTO p;   IF (q-p)>0 THEN     ret = c + (q-p)||'' days'';   ELSE     ret = c + ((q-p)+7)||'' days'';   END IF;   RETURN RET;  END;  ' LANGUAGE 'plpgsql';